Method and apparatus for receiving or transmitting data

ABSTRACT

A base station divides a subframe into a downlink time duration for downlink, an uplink time duration for uplink, and a guard period between the downlink time duration and the uplink time duration. The base station transmits a downlink control channel including information on a downlink packet duration allocated for downlink transmission of a terminal and information on an uplink packet duration allocated for uplink transmission of the terminal to the terminal in the downlink time duration.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation Application of U.S. patentapplication Ser. No. 15/410,966 filed Jan. 20, 2017, which claimspriority to and the benefit of Korean Patent Applications Nos.10-2016-0008086, 10-2016-0041938, 10-2016-0059069, 10-2016-0093882,10-2016-0103246, 10-2016-0126987, 10-2016-0147020, and 10-2017-0002019filed in the Korean Intellectual Property Office on 22 Jan. 2016, 5 Apr.2016, 13 May 2016, 25 Jul. 2016, 12 Aug. 2016, 30 Sep. 2016, 4 Nov.2016, and 5 Jan. 2017, respectively, the entire contents of which areincorporated herein by reference.

BACKGROUND (a) Field

The present invention generally relates to a method and apparatus fortransmitting or receiving data.

(b) Description of the Related Art

Among wireless communication schemes, frequency division duplexing (FDD)uses continuous frequency resources, i.e., continuous spectrums, amongwireless resources. For example, spectrum 1 may be set as a downlinkresource transmitted by a base station and received by a mobile station,and spectrum 2 may be set as an uplink resource transmitted by a mobilestation and received by a base station. In this case, the same radioframe is repeated in each spectrum. One radio frame includes a pluralityof sub-frames, and the sub-frame may be a minimum unit in time forscheduling. The FDD scheme requires at least two spectrums, i.e., apaired spectrum, and cannot be applied when only one spectrum, i.e., anunpaired spectrum, is used.

Time division duplexing (TDD) is a scheme in which transmission andreception of the base station and the terminal are mixed in onespectrum. One subframe may be a downlink subframe for transmission bythe base station or an uplink subframe for transmission by the terminal.Such a TDD scheme may form different radio frames according to the orderand combination of the downlink subframes and uplink subframes. Sincethe TDD scheme can allocate the spectrum as one unit, it can be appliednot only to the unpaired spectrum but also to the paired spectrum.

In a case of the unpaired spectrum, retransmission, for example a hybridautomatic repeat request (HARQ) procedure, may be complicated. In theTDD scheme, there is a case where the downlink subframe does notcorrespond one-to-one with the uplink subframe. In this case, themany-to-one correspondence relationship should be defined in advance. Inthe case of the TDD scheme in which the number of downlink subframes ismore than the number of uplink subframe, one uplink subframe transmitsHARQ ACKs for several downlink subframes. In the case of the TDD schemein which the number of uplink subframes is more than the number ofdownlink subframe, one downlink subframe transmits HARQ ACKs for severaluplink subframes.

Therefore, the base station should wait for a specific uplink subframeincluding the HARQ ACK to confirm whether the terminal decodes themessage transmitted by the base station. The terminal also should waitfor a specific downlink subframe including the HARQ ACK in the uplinkHARQ. This affects the latency of wireless communications and istherefore not suitable for a service for transmitting messages in aparticularly short time.

SUMMARY

An embodiment of the present invention provides a method and apparatusfor transmitting and receiving data applicable to a wirelesscommunication system capable of operating in an unpaired spectrum.

According to an embodiment of the present invention, a method oftransmitting or receiving data by a terminal in a wireless communicationsystem using a radio frame including a plurality of subframes isprovided. The method includes receiving a downlink control channel froma base station in a downlink time duration of a first subframe andreceiving a downlink packet in the downlink packet duration from thebase station. The first subframe is divided into the downlink timeduration for downlink, an uplink time duration for uplink, and a guardperiod between the downlink time duration and the uplink time duration.The downlink control channel includes information on a downlink packetduration allocated for downlink transmission of the terminal andinformation on an uplink packet duration allocated for uplinktransmission of the terminal.

The downlink control channel may further include a timing fortransmitting an ACK/NACK feedback for the downlink packet by theterminal.

The timing may indicate a k-th subframe from the first subframe. Here, kis an integer equal to or greater than one.

The method may further include receiving information on a set ofdownlink packet durations and a set of uplink packet durations from thebase station through a higher layer signaling. The information on thedownlink packet duration may indicate an element of the set of downlinkpacket durations, and the information on the uplink packet duration mayindicate an element of the set of uplink packet durations.

The information on the downlink packet duration may include a number ofsymbols included in the downlink packet duration and a start symbolindex offset of the downlink packet duration.

The information on the uplink packet duration may include a number ofsymbols included in the uplink packet duration and a value indicating atransmission timing for the uplink packet duration.

The value may include a symbol index offset to be applied to a timingadvance assigned to the terminal.

The information on the downlink packet duration may include an index ofthe downlink packet duration and a length of the downlink packetduration, and the information on the uplink packet duration may includean index of the uplink packet duration to be applied to a timing advanceassigned to the terminal and a length of the uplink packet duration.

The downlink control channel may be transmitted at a beginning of thefirst subframe, and the method may further include receiving a seconddownlink control channel including additional information on thedownlink packet duration or the uplink packet duration on apredetermined symbol of the downlink time duration.

The method may further include receiving a third downlink controlchannel including information on a length of the downlink time durationof the first subframe from the base station, and monitoring the downlinkcontrol channel or the second downlink control channel within thedownlink time duration of the first subframe in a case of monitoring thedownlink control channel or the second downlink control channel.

A downlink packet duration for downlink transmission of another terminalor an uplink packet duration for uplink transmission of another terminalmay be allocated to the guard period.

A second subframe adjacent to the first subframe may include a seconddownlink time duration for downlink and a second uplink time durationfor uplink in different order from the first subframe.

According to another embodiment of the present invention, a method oftransmitting or receiving data by a base station in a wirelesscommunication system using a radio frame including a plurality ofsubframes is provided. The method includes dividing a subframe into adownlink time duration for downlink, an uplink time duration for uplink,and a guard period between the downlink time duration and the uplinktime duration, and transmitting to the terminal a downlink controlchannel including information on a downlink packet duration allocatedfor downlink transmission of a terminal and information on an uplinkpacket duration allocated for uplink transmission of the terminal in thedownlink time duration.

According to yet another embodiment of the present invention, anapparatus for transmitting or receiving data in a wireless communicationsystem using a radio frame including a plurality of subframes isprovided. The apparatus includes a receiver, a transmitter, and acontroller. The receiver receives a downlink control channel from a basestation in a downlink time duration of a subframe. The subframe isdivided into the downlink time duration for downlink, an uplink timeduration for uplink, and a guard period between the downlink timeduration and the uplink time duration. The downlink control channelincludes information on a downlink packet duration allocated fordownlink transmission of the apparatus and information on an uplinkpacket duration allocated for uplink transmission of the apparatus. Thetransmitter transmits an uplink packet in the uplink packet duration tothe base station. The controller controls the receiver and thetransmitter.

According to still another embodiment of the present invention, anapparatus for transmitting or receiving data in a wireless communicationsystem using a radio frame including a plurality of subframes isprovided. The apparatus includes a processor and a transmitter. Theprocessor divides a subframe into a downlink time duration for downlink,an uplink time duration for uplink, and a guard period between thedownlink time duration and the uplink time duration. The transmittertransmits to the terminal a downlink control channel includinginformation on a downlink packet duration allocated for downlinktransmission of a terminal and information on an uplink packet durationallocated for uplink transmission of the terminal to in the downlinktime duration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a wireless communication system according toan embodiment of the present invention.

FIG. 2 shows a radio frame structure according to an embodiment of thepresent invention.

FIG. 3 is a flowchart showing a method of scheduling an ST subframe in awireless communication system according to an embodiment of the presentinvention.

FIG. 4 shows a method for transmitting or receiving data using an STsubframe in a wireless communication system according to an embodimentof the present invention.

FIG. 5 is shows another method of transmitting a downlink controlchannel in a wireless communication system according to an embodiment ofthe present invention.

FIG. 6, FIG. 7, and FIG. 8 show an ST subframe configuration betweenbase stations in a wireless communication system according to anembodiment of the present invention.

FIG. 9, FIG. 10, FIG. 11, FIG. 12 and FIG. 13 each show a downlinktransmission method in a wireless communication system according to anembodiment of the present invention.

FIG. 14 and FIG. 15 each show a method of transmitting an uplink HARQfeedback in a wireless communication system according to an embodimentof the present invention.

FIG. 16, FIG. 17, FIG. 18, and FIG. 19 each show an uplink transmissionmethod in a wireless communication system according to an embodiment ofthe present invention.

FIG. 20 shows another example of an ST subframe structure in a wirelesscommunication system according to an embodiment of the presentinvention.

FIG. 21 and FIG. 22 each show a method of transmitting a downlink HARQfeedback in a wireless communication system according to an embodimentof the present invention.

FIG. 23 shows a terminal-specific ST subframe in a wirelesscommunication system according to an embodiment of the presentinvention.

FIG. 24 is a flowchart showing a method of scheduling an ST subframe ina wireless communication system according to an embodiment of thepresent invention.

FIG. 25 and FIG. 26 each show an ST subframe without a guard interval ina wireless communication system according to an embodiment of thepresent invention.

FIG. 27 shows a transmission method using an ST subframe in a wirelesscommunication system according to an embodiment of the presentinvention.

FIG. 28 shows an ST subframe configured for each subband in a wirelesscommunication system according to an embodiment of the presentinvention.

FIG. 29 shows an example of a transmission method using a plurality ofscheduling types in a wireless communication system according to anembodiment of the present invention.

FIG. 30 and FIG. 31 each show an example of a low-latency traffictransmission method in a wireless communication system according to anembodiment of the present invention.

FIG. 32 shows a radio frame structure used in a wireless communicationsystem according to another embodiment of the present invention.

FIG. 33 shows forward subframe configurations in a radio frame structureaccording to another embodiment of the present invention.

FIG. 34 shows reverse subframe configurations in a radio frame structureaccording to another embodiment of the present invention.

FIG. 35 shows aggregated subframe configurations in a radio framestructure according to another embodiment of the present invention.

FIG. 36 and FIG. 37 each show a downlink transmission method in awireless communication system according to another embodiment of thepresent invention.

FIG. 38 and FIG. 39 each show a downlink transmission method using anaggregated subframe in a wireless communication system according toanother embodiment of the present invention.

FIG. 40 and FIG. 41 each show an uplink transmission method using anaggregated subframe in a wireless communication system according toanother embodiment of the present invention.

FIG. 42, FIG. 43, FIG. 44 and FIG. 45 each show a method of transmittingan uplink HARQ feedback in a wireless communication system according toanother embodiment of the present invention.

FIG. 46 shows a method of transmitting a sounding reference signal in awireless communication system according to another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following detailed description, only certain embodiments of thepresent invention have been shown and described, simply by way ofillustration. As those skilled in the art would realize, the describedembodiments may be modified in various different ways, all withoutdeparting from the spirit or scope of the present invention.Accordingly, the drawings and description are to be regarded asillustrative in nature and not restrictive. Like reference numeralsdesignate like elements throughout the specification.

In the specification, a term “terminal” may designate a user equipment(UE), a mobile station (MS), a mobile terminal (MT), an advanced mobilestation (AMS), a high reliability mobile station (HR-MS), a subscriberstation (SS), a portable subscriber station (PSS), an access terminal(AT), and so on, or may include all or some functions thereof.

Further, a term “base station” (BS) may designate a node B, an evolvednode B (eNB), a gNB, an advanced base station (ABS), a high reliabilitybase station (HR-BS), an access point (AP), a radio access station(RAS), a base transceiver station (BTS), an mobile multihop relay (MMR)BS, a relay station (RS) functioning as the BS, a relay node (RN)functioning as the BS, a high reliability relay station (HR-RS)functioning as the BS, a small BS [e.g., a femto BS, a pico BS, a macroBS, a micro BS, a home node B (HNB), a home eNB (HeNB), a home gNB(HgNB)], and so on, or may include all or some functions thereof.

FIG. 1 schematically shows a wireless communication system according toan embodiment of the present invention.

Referring to FIG. 1, a wireless communication system includes aplurality of base stations 100 and a plurality of terminals 200.

The base station 100 transmits a synchronization signal and a referencesignal, and the terminal 200 recovers the message transmitted by thebase station 100 using the synchronization signal and the referencesignal received from the base station 100. The terminal 200 alsotransmits a synchronization signal and a reference signal, and the basestation 100 recovers a message transmitted by the terminal 200 using thesynchronization signal and the reference signal received from theterminal 200. The base station 100 may define a control channel forefficiently managing the plurality of terminals 200 and indicate radioresources to be used for transmission and reception of the terminals 200through the control channel.

The base station 100 includes a processor 110, a transmitter 120, and areceiver 130. The processor 110 implements a higher layer 111 and aphysical layer 112, and may execute commands necessary for operations ofthe base station 100 to be described below and control operations of thetransmitter 120 and the receiver 130. The transmitter 120 transmits asignal delivered from the physical layer 112 to the terminal 200 via anantenna. The receiver 130 receives a signal from the terminal 200 via anantenna and transfers the signal to the physical layer 112. Thetransmitter 120 and the receiver 130 may exchange signals with otherbase stations 100.

Similarly, the terminal 200 includes a processor 210, a transmitter 220,and a receiver 230. The processor 210 implements a higher layer 211 anda physical layer 212, and may execute commands necessary for operationsof the terminal 200 to be described below and control operations of thetransmitter 120 and the receiver 130. The transmitter 220 transmits asignal delivered from the physical layer 212 to the base station 100 viaan antenna. The receiver 230 receives a signal from the terminal 100 viaan antenna and transfers the signal to the physical layer 212. Thetransmitter 220 and the receiver 230 may exchange signals with otherterminals 200.

In some embodiments, another device 300 for managing the plurality ofbase stations 100 may be provided. The device 300 may manage radioresources such that the radio resources do not collide with each otheramong the plurality of base stations 100.

Next, a radio frame used in a wireless communication system according toan embodiment of the present invention is described with reference toFIG. 2.

FIG. 2 shows a radio frame structure according to an embodiment of thepresent invention.

Referring to FIG. 2, a radio frame includes a plurality of subframes. Asubframe may be referred to as a slot. According to an embodiment of thepresent invention, a certain subframe among the plurality of subframesis divided into a downlink and an uplink in time resources. Hereinafter,such a subframe is referred to as an “ST subframe.”

The ST subframe includes a downlink time duration DwPTS and an uplinktime duration UpPTS. The ST subframe further includes a guard period(GP) between the downlink time duration DwPTS and the uplink timeduration UpPTS. The downlink time duration consists of consecutivetransmission of downlink symbols, and the uplink time duration consistsof consecutive transmission of uplink symbols. The guard period GP maybe set in consideration of a propagation delay and a delay spread.

In some embodiments, the downlink symbol and the uplink symbol may referto a symbol based on multi-carrier modulation. The numerology applied tomulti-carrier modulation may be one or several (e.g., 15 kHz, 30 kHz).If multiple numerologies coexist on a single system carrier, the lengthof the guard period GP may vary depending on numerologies because asymbol length may vary.

A downlink control channel is transmitted in the downlink time duration.In some embodiments, the downlink control channel may be transmittedperiodically. For example, the downlink control channel may betransmitted for each ST subframe or for each slot. Downlink datascheduling or uplink data scheduling may be performed through thedownlink control channel.

A downlink packet may be transmitted during a downlink packet durationallocated to a terminal in the downlink time duration, and an uplinkpacket may be transmitted during an uplink packet duration allocated tothe terminal in the uplink time duration. The downlink packet durationmay be called a downlink sub-slot or a downlink transmission timeinterval (TTI), and the uplink packet duration may be called an uplinksub-slot or an uplink TTI. The sub-slot may also be referred to as amini-slot.

In one embodiment, an aperiodic downlink control channel may be furthertransmitted between the periodically transmitted downlink controlchannels. Furthermore, the periodic downlink control channel and theaperiodic downlink control channel may independently perform thedownlink data scheduling or the uplink data scheduling. Alternatively,the downlink data scheduling or the uplink data scheduling may beperformed only when both the periodic downlink control channel and theaperiodic downlink control channel are received.

In some embodiments, an ST subframe having uplink symbols and downlinksymbols in a different order from the ST subframe shown in FIG. 2 may bedefined. Such an ST subframe is referred to as a “reverse subframe.” Inthis case, an interval between the uplink time duration and the downlinktime duration may be determined in consideration of a circuit switchingdelay. As described above, an ST subframe in which a downlink timeduration precedes an uplink time duration is referred to as a “forwardsubframe.”

The ST subframe may be variously set according to the number of downlinksymbols and the number of uplink symbols. An ST subframe set consistingof possible combinations of ST subframes may be defined. Assuming thatthe number of cases for the number of downlink symbols used in the STsubframe is ND and the number of cased for the number of uplink symbolsis NU, the number of possible combinations of ST subframes is ND*NU. Insome embodiments, if the downlink symbol is defined as several types andthe uplink symbol is defined as several types, the number of possiblecombinations of ST subframes may be ND*NU multiplied by the number ofsymbol type combinations.

In one embodiment, a base station (100 in FIG. 1) may select a maximumnumber of downlink symbols and a maximum number of uplink symbols, andshare the selected maximum number of downlink symbols and the maximumnumber of uplink symbols with adjacent base stations 100 throughsignaling. Accordingly, the base station 100 can potentially preventinterference between terminals (200 in FIG. 1) without interfering withother adjacent base stations 100. In another embodiment, a device (300of FIG. 1) that manages a plurality of base stations 100 may determinethe maximum number of downlink symbols and the maximum number of uplinksymbols, and forwards them to the base stations 100 such that the basestations 100 can share the maximum number of downlink symbols and themaximum number of uplink symbols. In another embodiment, some basestations 100 among the plurality of base stations 100 may determine themaximum number of downlink symbols and the maximum number of uplinksymbols, and may transmit them to the adjacent base stations 100. Thebase station 100 may determine the maximum number of downlink symbolsand the maximum number of uplink symbols among the maximum number set ofdownlink symbols and the maximum number set of uplink symbolstransmitted.

In some embodiments, the base station 100 may forward the ST subframeconfiguration to the terminal through a higher layer configuration,i.e., higher layer signaling. In another embodiment, the ST subframeconfiguration may be transmitted to the terminal 100 through dynamicscheduling, i.e., a downlink control channel.

The terminal 200 may support both low latency traffic and high latencytraffic. The base station may use a radio frame including a plurality ofST subframes to support the low latency traffic. FIG. 2 shows a casewhere all ten subframes of the radio frame are ST subframes. However,the number of subframes included in the radio frame is not limited tothis, and some of the subframes included in the radio frame may bedownlink subframes or uplink subframes.

For example, if a radio frame includes a downlink subframe, an uplinksubframe, and an ST subframe, the number of subframes necessary forreceiving an HARQ feedback after the base station transmits downlinkassignment may be different depending on a subframe index to which thedownlink assignment belongs. For example, when the downlink assignmentis transmitted on a downlink subframe, the HARQ feedback may be receivedon an uplink subframe following the downlink subframe or an uplink timeduration of an ST subframe following the downlink subframe. However,when the downlink assignment is transmitted on an ST subframe, the HARQfeedback can be transmitted in the same ST subframe if the guard periodis set to a time longer than the minimum time necessary for transmittingthe HARQ feedback after receiving data.

The base station may adjust the downlink time duration and the uplinktime duration in the ST subframe according to a ratio between thedownlink traffic and the uplink traffic or the interference ofneighboring devices. This may be performed in the higher layer of thebase station.

Next, a method of scheduling an ST subframe to the mobile station by thebase station is described with reference to FIG. 3 to FIG. 5.

FIG. 3 is a flowchart showing a method of scheduling an ST subframe in awireless communication system according to an embodiment of the presentinvention.

Referring to FIG. 3, in some embodiments, a base station transmitsinformation on a set of downlink packet durations and a set of uplinkpacket durations to a terminal (S310). In one embodiment, the basestation may transmit the information on the set of downlink packetdurations and the set of uplink packet durations to the terminal througha higher layer configuration, i.e., higher layer signaling.

If the terminal does not receive the higher layer configuration from thebase station in an initial access stage, the terminal may apply adownlink packet duration or a downlink packet duration and an uplinkpacket duration that are predefined in a standard and stored in theterminal in order to receive system information. After the terminalreceives the higher layer configuration from the base station, theterminal can receive a packet by applying the correspondingconfiguration information.

When the information on the packet duration of the terminal isreconfigured through the higher layer configuration from the basestation, the terminal may apply the downlink packet duration or thedownlink packet duration and the uplink packet duration that arepredefined in the standard and stored in the terminal

In some embodiments, the set of downlink packet durations may include aset of downlink symbol numbers used by the downlink packet and a set ofdownlink symbol index offsets that start demodulating the downlinkpacket. The set of uplink packet durations may include a set of uplinksymbol numbers used by the uplink packet and a set of uplink symbolindex offsets of additional timing advance applied to the uplink packet.

In some embodiments, the set of downlink packet durations may include aset of indexes of the downlink packet duration, and the set of uplinkpacket durations may include a set of indexes of the uplink packetduration. In one embodiment, the set of downlink packet durations mayfurther include a set of lengths of the downlink packet duration, andthe set of uplink packet durations may further include a set of lengthsof the uplink packet duration. In one embodiment, the downlink packetduration may correspond to a downlink sub-slot and the uplink packetduration may correspond to an uplink sub-slot. Alternatively, in a casewhere the subframe includes a plurality of slots, for example, twoslots, the downlink packet duration may correspond to a downlink slotand the uplink packet duration may correspond to an uplink slot.

Referring to FIG. 3 again, the base station transmits information on adownlink packet duration selected from the set of downlink packetdurations and information on an uplink packet duration selected from theset of uplink packet durations to the terminal (S320 and S330). The basestation may transmit the information on the downlink packet durationthrough a downlink assignment of a downlink control channel (S320), andmay transmit the information on the uplink packet duration through anuplink grant of the downlink control channel (S330). That is, thedownlink control information (DCI) of the downlink control channel fordownlink assignment may include the information on the downlink packetduration, and the DCI of the downlink control channel for the uplinkgrant may include the information on the uplink packet duration. Thedownlink control channel may be, for example, a physical downlinkcontrol channel (PDCCH).

In some embodiments, the base station may transmit to the terminalinformation indicating a downlink symbol number (the number of downlinksymbols) selected from the set of downlink symbol numbers, a downlinksymbol index offset selected from the set of downlink symbol indexoffsets, an uplink symbol number (the number of uplink symbols) selectedfrom the set of uplink symbol numbers, and an uplink symbol index offsetselected from the set of uplink symbol index offsets.

In one embodiment, the base station may transmit information indicatingthe selected downlink symbol number, information indicating the selecteddownlink symbol index offset, information indicating the selected uplinksymbol number, and information indicating the selected uplink symbolindex offset.

In another embodiment, the base station may define a plurality of STsubframes defined by various combinations of the downlink symbol number,the downlink symbol index offset, the uplink symbol number, and theuplink symbol index offset, and transmit information indicating an STsubframe selected from the plurality of ST subframes.

In yet another embodiment, the base station may define a plurality ofdownlink packet durations defined by various combinations of thedownlink symbol number and the downlink symbol index offset, andtransmit information for indicating a downlink packet duration selectedfrom the plurality of downlink packet durations. The base station maydefine a plurality of uplink packet durations defined by variouscombinations of the uplink symbol number and the uplink symbol indexoffset, and transmit information indicating an uplink packet durationselected from the plurality of uplink packet durations.

In some embodiments, the base station may transmit to the terminalinformation indicating a downlink packet duration index selected fromthe set of downlink packet duration indexes and information indicating alength of the downlink packet duration, and transmit to the terminalinformation indicating an uplink packet duration index selected from theset of uplink packet duration indexes and information indicating alength of the uplink packet duration.

On the other hand, the set of downlink symbol numbers may have NDelements. For example, the downlink packet duration may have TD_(i)downlink symbols among TD downlink symbols, and TD_(i) corresponds toone element of {TD₁, TD₂, . . . TD_(ND)} set. Here, TD_(ND) may be equalto TD, and TD₁ to TD_(ND-1) may have a value smaller than TD.

In this case, the ND elements include one normal downlink packetduration and (ND-1) reduced downlink packet durations. Here, if ND is 1,only the normal downlink packet duration may be supported. The normaldownlink packet duration occupies the TD downlink symbols whichcorrespond to the downlink time duration. The reduced downlink packetduration occupies a smaller number of downlink symbols than the TDdownlink symbols. In some embodiments, the reduced downlink packetduration may be used to decode the low latency downlink traffic and tosecure processing time for generating an uplink HARQ feedback. Thereduced downlink packet duration may be referred to as a short downlinkTTI. In one embodiment, the reduced downlink packet duration may also beapplied to high latency downlink traffic.

In some embodiments, the base station may generate another set ofdownlink symbol numbers with elements supported by the terminal from the{TD₁, TD₂, . . . TD_(ND)} set and inform the generated set to theterminal. When the terminal cannot support all the elements of the {TD₁,TD₂, . . . TD_(ND)} set depending on the processing capability of theterminal or it is not necessary to support unnecessary elementsaccording to the communication service scenario, the base station maygenerate the set with only some elements.

In one embodiment, when one downlink packet duration is operated, thebase station may not transmit the set of downlink symbol numbers to theterminal.

The set of uplink symbol numbers may have NU elements. For example, theuplink packet duration may have TU_(j) uplink symbols among TU uplinksymbols, and TU_(j) corresponds to one element of {TU_(j), TU₂, . . .TU_(NU)} set. Here, TU_(NU) may be equal to TU, and TU₁ to TU_(NU-1) mayhave a value smaller than TU.

In this case, the NU elements include one normal uplink packet durationand (NU-1) reduced uplink packet durations. Here, if NU is 1, onlynormal uplink packet duration may be supported. The normal uplink packetduration occupies the TU uplink symbols which correspond to the uplinktime duration. The reduced uplink packet duration occupies a smallernumber of uplink symbols than the TU uplink symbols.

In some embodiments, the base station may generate another set of uplinksymbol numbers with elements supported by the terminal from the {TU₁,TU₂, . . . TU_(NU)} set and inform the generated set to the terminal.When the terminal cannot support all the elements of the {TU₁, TU₂, . .. TU_(NU)} set depending on the processing capability of the terminal orit is not necessary to support unnecessary elements according to thecommunication service scenario, the base station may generate the setwith only some elements.

In one embodiment, when one uplink packet duration is operated, the basestation may not transmit the set of uplink symbol numbers to theterminal.

In one embodiment, the terminal may set uplink transmission timing basedon an uplink symbol index offset received through the uplink grant andtiming advance received through a MAC control element. In oneembodiment, the terminal may set a value obtained by subtracting theuplink symbol index offset from the timing advance to effective timingadvance, and transmit the uplink packet in the effective timing advance.

On the other hand, a sum of the downlink symbol number TD and the uplinksymbol number TU is smaller than a length of one subframe. In someembodiments, there may be a case where the base station does not need toallocate a downlink packet or an uplink packet to the terminal in onesubframe.

In one embodiment, the base station may designate the uplink symbolnumber TU to zero and allocate only downlink packets. In this case, thedownlink time duration may be the same as one subframe. If a guardperiod is required, the downlink time duration may be shorter than onesubframe and the guard period may be allocated after the downlink timeduration. This subframe may be referred to as a DL-centric subframe. Insome embodiments, fixed downlink resources may be used. That is, thedownlink resources may be defined such that the terminal can assume thatthe base station always assigns downlink control information or downlinkdata to some downlink symbols and some subcarriers belonging to asubframe.

In another embodiment, the base station may allocate TD downlink symbolsonly to downlink control information and a guard period with apredetermined length. Here, TD is greater than zero. The base stationmay allocate TU uplink symbols for uplink packets to a remaining part ofthe subframe. Such a subframe may be referred to as a UL-centricsubframe.

FIG. 4 shows a method for transmitting or receiving data using an STsubframe in a wireless communication system according to an embodimentof the present invention.

Referring to FIG. 4, it is assumed that a base station NB communicateswith a plurality of terminals UE1 and UE2.

In FIG. 4, it is assumed that the terminal UE1 is assigned TD₂ as thenumber of downlink symbols, TD₁ as a downlink symbol index offset, TU₂as the number of uplink symbols, and 0 as an uplink symbol index offset.It is assumed that the terminal UE2 is assigned TD₁ as the number ofdownlink symbols, 0 as a downlink symbol index offset, TU_(j) as thenumber of uplink symbols, and TU₂ as an uplink symbol index offset. Insome embodiments, each of the terminals UE1 and UE2 may know a downlinkpacket duration (for example, the number of downlink symbols occupied bya downlink packet and a downlink symbol index offset) and an uplinkpacket duration (the number of uplink symbols occupied by an uplinkpacket and an uplink symbol index offset) through downlink assignmentand uplink grant. The terminals UE1 and UE2 may also know timingadvances TA₁ and TA₂ through a MAC information element. In someembodiments, transmit powers used by the terminals UE1 UE2 may bedetected from the downlink assignment.

Then, in order to receive a downlink packet transmitted by the basestation NB, the terminal UE1 demodulates the downlink packet of TD₂downlink symbols after the downlink symbol index offset TD₁ from thedownlink control channel CTRL. At this time, the terminal UE1 mayreceive the downlink control channel CTRL after a propagation delay PD1between the base station NB and the terminal UE1. Further, since theuplink symbol index offset is 0, the terminal UE1 transmits an uplinkpacket using TU₂ uplink symbols in accordance with the received timingadvance TA₁.

In order to receive a downlink packet transmitted by the base stationNB, the other terminal UE2 demodulates the downlink packet of TD₁downlink symbol from a time point when the start symbol index offset iszero. That is, the terminal UE2 demodulates the downlink packet from thedownlink symbols received consecutively after the downlink controlchannel CTRL. At this time, the terminal UE2 may receive the downlinkcontrol channel CTRL after a propagation delay PD2 between the basestation NB and the terminal UE2. The terminal UE2 sets a valuereflecting the uplink symbol index offset TU₂ to the received timingadvance TA₂ to an effective timing advance ETA₂ and transmits an uplinkpacket in accordance with the effective timing advance ETA₂. At thistime, the effective timing advance ETA₂ may be set to a value obtainedby subtracting the uplink symbol index offset TU₂ from the receivedtiming advance TA₂.

Although not shown in FIG. 4, TU (=TU₁+TU₂) uplink symbols may beallocated to other terminal. This terminal may transmit an uplink packetusing TU uplink symbols in accordance with the timing advance.

FIG. 5 is shows another method of transmitting a downlink controlchannel in a wireless communication system according to an embodiment ofthe present invention.

Referring to FIG. 5, in some embodiments, a downlink control channelCTRL2 may be transmitted in a predetermined set of symbol(s) in asubframe. This predetermined symbol may correspond to the beginning of asubframe or a downlink time duration. The base station may control adownlink packet DLP by transmitting downlink assignment or control anuplink packet ULP by transmitting uplink grant, through the downlinkcontrol channel CTRL2. In one embodiment, the downlink control channelCTRL2 may coexist with the downlink packet DLP in a time divisionmultiplexing (TDM) scheme or a frequency division multiplexing (FDM)scheme.

In some embodiments, the base station may transmit a first downlinkcontrol channel CTRL1 at the beginning of the subframe and furthertransmit a second downlink control channel CTRL2 at a predetermined setof symbol(s) in the subframe. In one embodiment, the second downlinkcontrol channel CTRL2 may include downlink assignment or uplink grant inthe same manner as the first downlink control channel CTRL1. Therefore,the base station may perform scheduling using only one of the firstdownlink control channel CTRL1 and the second downlink control channelCTRL2. In another embodiment, the first downlink control channel CTRL1and the second downlink control channel CTRL2 may support step-wisescheduling. In this case, the terminal may demodulate downlinkassignment or uplink grant information only when receiving both thefirst downlink control channel CTRL1 and the second downlink controlchannel CTRL2. For this, the first downlink control channel CTRL1 andthe second downlink control channel CTRL2 may transmit differentinformation. For example, the first downlink control channel CTRL1 maytransfer a resource block assignment and an HARQ identifier (ID), andthe second downlink control channel CTRL2 may transfer a modulation andcoding scheme (MCS).

In some embodiments, the base station may indicate to the terminalthrough the first downlink control channel CTRL1 whether to perform amonitoring operation of the second downlink control channel CTRL2. Atthis time, the base station may indicate, in the terminal-specificmanner, whether to perform the monitoring operation of the seconddownlink control channel CTRL2.

In some embodiments, the base station may transmit a third downlinkcontrol channel to the terminal every ST subframe or every slot. Thethird downlink control channel may be called a physical subframe typeindication channel (PSTICH).

In one embodiment, the PSTICH may include information a length of adownlink time duration. The PSTICH may be transmitted as a cell-specificmessage such that the terminal in an idle state can receive the PSTICH.Accordingly, the terminal can monitor the first downlink control channelCTRL1 or the second downlink control channel CTRL2 within the downlinktime duration identified by the PSTICH. Alternatively, upon receivingthe PSTICH, the terminal may not receive the first downlink controlchannel CTRL1 and the second downlink control channel CTRL2. That is,after receiving the PSTICH, the terminal may determine whether tofurther receive the first or second downlink control channels CTRL1 andCTRL2. Then, the terminal can receive a downlink packet from the basestation based on the downlink time duration indicated by the PSTICH.

In another embodiment, the PSTICH may indicate to the terminal whetherto perform the monitoring operation of the first or second downlinkcontrol channel CTRL1 or CTRL2. The PSTICH may indicate a downlinksymbol on which the first or second downlink control channel CTRL1 orCTRL2 is transmitted in the subframe. Accordingly, the terminal monitorsthe first downlink control channel CTRL1 or the second downlink controlchannel CTRL2 on the predetermined set of symbol(s). The base stationmay configure different terminals to monitor the first downlink controlchannel CTRL1 or the second downlink control channel CTRL2 on differentsymbols. As such, the base station can control the monitoring of thesecond downlink control channel CTRL2 through the transmission of thePSTICH, which can help battery management of the terminal.

In yet another embodiment, the terminal may receive the PSTICH ofadjacent base station to recognize the subframe or slot type. Theterminal may separate the CSI (channel estimation information)estimation with respect to the slot type of the adjacent base station.For example, the terminal may be configured to estimate K distinct CSIsubframe set (or slot set) or CSI process. In other words, the terminalmay distinguish K distinct interference hypotheses depending oncombinations of the slot type of adjacent base stations. For example,three adjacent base stations operate the dynamic TDD and the terminal isconfigured to monitor 8 CSI subframe set or 8 CSI processes. Theterminal may notice a specific subframe set or a specific CSI process byreceiving the PSTICH of each adjacent base station.

An ST subframe configuration between different base stations isdescribed with reference to FIG. 6 to FIG. 8.

FIG. 6, FIG. 7, and FIG. 8 show an ST subframe configuration betweenbase stations in a wireless communication system according to anembodiment of the present invention.

Referring to FIG. 6 and FIG. 7, in some embodiments, an ST subframeconfiguration may be set such that a downlink time duration DwPTS and anuplink time duration UpPTS do not overlap with each other betweenneighboring base stations NB1 and NB2, in order to reduce uplink anddownlink interferences. For example, in a case where an uplink timeduration UpPTS of the base station NB1 overlaps with a downlink timeduration DwPTS of the base station NB2, an interference may occurbecause the base station NB1 can receive a downlink packet of the basestation NB2 when receiving an uplink packet from the terminal in theuplink time duration UpPTS. Therefore, the interference can be preventedby configuring ST subframes so that the downlink time duration DwPTS andthe uplink time duration UpPTS do not overlap with each other betweenthe neighboring base stations NB1 and NB2.

In this case, as shown in FIG. 6, if subframe boundaries of the basestations NB1 and NB2 do not match with each other, an interference mayoccur. For example, when a subframe boundary offset occurs, a subframeof the base station NB1 may be an uplink time duration UpPTS and asubframe of the base station NB2 may be a downlink time duration DwPTS.Then, since the base station NB1 receives both an uplink packet of theterminal and a downlink packet of the base station NB2, a demodulationquality of the uplink packet from the terminal may deteriorate.Therefore, in another embodiment, as shown in FIG. 7, the subframeboundaries may be aligned between the ST subframes of the base stationsNB1 and NB2.

Referring to FIG. 8, in some embodiments, base stations NB1 and NB2 mayuse different ST subframes. In this case, an interference may occur whenthe base station NB1 allocates a downlink time duration DwPTS for a longtime and the base station NB2 allocates an uplink time duration UpPTSfor a long time. That is, a timing when a terminal UE1 communicatingwith the base station NB1 receives a downlink packet from the basestation NB1 may be a timing when a propagation delay and a delay spreadhave elapsed after the base station NB1 transmits the downlink packet. Atiming when a terminal UE2 communicating with the base station NB2transmits an uplink packet may be a timing when the base station NB2instructs the timing advance. Therefore, when the two terminals UE1 andUE2 are adjacent to each other, a subframe direction mismatch may occurssuch that the terminal UE1 can simultaneously receive the downlinkpacket of the base station NB1 and the uplink packet of the UE2.Consequently, a decoding performance of the downlink packet maydeteriorate. In some embodiments, the neighboring base stations NB1 andNB2 may share a maximum propagation delay and a maximum timing advanceand set a separate propagation delay and a separate timing advance foreach of the terminals UE1 and UE2 such that the subframe directionmismatch can be avoided.

Next, a downlink transmission method using a radio frame according to anembodiment of the present invention is described with reference to FIG.9 to FIG. 15.

FIG. 9, FIG. 10, FIG. 11, FIG. 12 and FIG. 13 each show a downlinktransmission method in a wireless communication system according to anembodiment of the present invention.

Referring to FIG. 9, FIG. 10, FIG. 11 and FIG. 12, when a base stationtransmits a downlink packet DLP in a downlink time duration of an STsubframe to a terminal, a terminal may transmit an HARQ feedback in anuplink time duration of the same ST subframe. Hereinafter, the HARQfeedback for the downlink packet DLP is referred to as an “uplink HARQfeedback.” The uplink HARQ feedback for each transport block may be anuplink HARQ ACK or an uplink HARQ NACK. For convenience, the uplink HARQfeedback is shown as an HARQ ACK in FIG. 9, FIG. 10, FIG. 11, and FIG.12.

As shown in FIG. 9, FIG. 10, and FIG. 11, the base station may transmita downlink control channel CTRL including a downlink assignment and anuplink grant to a terminal, and then transmits a downlink pack DLP aftera downlink symbol index offset DL_Offset. The terminal UE may transmitan uplink HARQ feedback in accordance with an effective timing advanceTA in the same ST subframe. FIG. 9 and FIG. 10 show a case where thedownlink control channel CTRL including the downlink assignment and theuplink grant is transmitted through a beginning downlink symbol(s) ofthe ST subframe, and FIG. 11 shows a case where the downlink controlchannel CTRL is transmitted through a downlink symbol(s) which is in themiddle of the ST subframe. Further, FIG. 9 shows a case where thedownlink symbol index offset DL_Offset has a value larger than 0, andFIG. 10 and FIG. 11 show a case where the downlink symbol index offsetis zero.

As shown in FIG. 12, the base station may transmit a downlink controlchannel CTRL and a downlink packet DLP in the same downlink symbol usingdifferent subcarriers to the terminal. The terminal may transmit anuplink HARQ feedback in accordance with an effective timing advance TA.

In some embodiments, a size of a downlink packet may be limited to apredetermined size or less in order to transmit an uplink HARQ feedbackin the same ST subframe as the downlink packet. To this end, a basestation may segment the downlink packet so that the size of eachdownlink packet is the predetermined size or less. Then, a time requiredfor a terminal to decode the downlink packet can be reduced. In thiscase, the base station may allocate a radio resource corresponding to asmall number of downlink symbols such that a short packet can beconfined to a short time but a sufficient bandwidth, and schedule theradio resource to the terminal. In one embodiment, the number ofdownlink symbols to be applied to short packet scheduling may beconfigured through a higher layer signalling. In this case, the numberof downlink symbols may be implicitly or explicitly indicated. Forexample, the number of downlink symbols may be implicitly indicated in amanner of the predetermined number of downlink symbols according totraffic types and explicitly indicating a specific traffic type, or thenumber of downlink symbols may be explicitly indicated. In anotherembodiment, the number of downlink symbols to be applied to the shortpacket scheduling may be included in the downlink assignment. Those setof downlink symbols may correspond to a downlink sub-slot.

It is possible to consider a case where different terminals supportdifferent traffic with different latency requirements in an environmentwhere several terminals served by the base station exist. For example, aterminal UEL supporting low latency traffic may have a short downlinkHARQ round trip time (RTT) and a short uplink HARQ RTT, and a longerHARQ RTT may be configured to a terminal UEH supporting high latencytraffic. The terminals UEL and UEH may receive the low latency trafficor the high latency traffic via a downlink assignment.

In some embodiments, a base station may transmit uplink HARQ feedbacktransmission timing of a terminal through a downlink control channel,for example, a DCI of the downlink control channel, or a higher layersignalling, or a combination of a DCI of the downlink control channeland a higher layer signalling. The transmission timing of the UL HARQfeedback may be calculated from a time point when a downlink packet isreceived. A unit of the transmission timing may be an uplink symbolindex, an uplink slot index, an uplink slot index, or an uplink subframeindex. The terminal UEL may be instructed to transmit the uplink HARQfeedback in the same slot as the slot where the downlink packet isreceived.

In order to support the terminals UEL and UEH supporting the differenttraffics types in one ST subframe, a TDM scheme or a scheme in whichboth the TDM scheme or an FDM scheme are applied may be used.

The base station may decrease a time between downlink assignmenttransmission and downlink packet transmission, to minimize a time fromwhen the terminal UEL receives the downlink assignment until ittransmits the uplink HARQ feedback. To this end, as shown in FIG. 9,FIG. 10 or FIG. 11 when transmitting a downlink control channel CTRLincluding the downlink assignment and a downlink packet DLP in differentdownlink symbols, the base station may transmit the downlink packet DLPin succession to the downlink control channel CTRL. In anotherembodiment, the base station may transmit the downlink control channelCTRL and the downlink packet DLP in the same downlink symbol as shown inFIG. 12.

In some embodiments, a base station may allocate a downlink controlchannel to a low downlink symbol index of the ST subframe to guarantee asufficient processing time for downlink packet decoding and uplink HARQfeedback generation of the terminal UEL. Then, the terminal can receivethe downlink packet at an early timing and acquire the processing time.When the downlink control channel and the downlink packet aretransmitted in different downlink symbols, the base station may transmitthe downlink packet on a downlink symbol subsequent to the downlinkcontrol channel such that the terminal can receive the downlink packetat the early timing.

If the base station allocates the downlink symbol subsequent to thedownlink control channel to the terminal UEL, downlink control channelreception and downlink packet reception may not occur consecutively inthe terminal UEH. Since the terminal UEL uses a small number of downlinksymbols to satisfy the low latency requirement, the base station mayallocate a radio resource to the terminal UEH using the remainingdownlink symbols. The terminal UEH may implicitly or explicitly receivea downlink symbol index offset indicating a start symbol allocated froma downlink assignment of a downlink control channel. For example, theterminal UE may implicitly estimate the downlink symbol index offsetfrom a scheduling type included in the downlink assignment, or mayexplicitly receive the downlink symbol index offset through the downlinkassignment. Therefore, as shown in FIG. 9, the terminal UEH can receivethe downlink control channel and then demodulate a downlink packet DLPon downlink symbols after the downlink symbol index offset DL_Offset.The downlink symbol index offset DL_Offset may have an explicit value oran implicit value indicating one of several predetermined values.

Referring to FIG. 13, when an FDM scheme and a TDM scheme are usedtogether, a base station may multiplex a terminal UEL supporting lowlatency traffic and a terminal UEH supporting high latency traffic inthe same downlink symbols. In an example shown in FIG. 13, somesubcarriers of TD₁ downlink symbols subsequent to a downlink controlchannel including a downlink assignment may be allocated to the terminalUEL such that the terminal UEL can demodulate a downlink packet DLP1transmitted through the TD₁ downlink symbols. In this case, somesubcarriers of TD₂ downlink symbols after the TD₁ downlink symbols maybe allocated to a terminal UEH as a radio resource, or some subcarriersthat are not allocated to the terminal UEL among TD (TD=TD₁+TD₂)downlink symbols subsequent to the downlink control channel may beallocated to the terminal UEH as the radio resource. The terminal UEHmay identify which type of radio resource is used from the downlinkassignment. That is, the terminal UEH may confirm TD₁, TD₂, or TD, andsubcarriers from the downlink assignment. When the terminal UEH uses theTD₂ downlink symbols, the terminal UEH may demodulate a downlink packetDLP2 from the TD₂ downlink symbols starting from the (1+TD₁)-th downlinksymbol. The terminal UEH may demodulate a downlink packet DLP3 from theTD downlink symbols following the downlink control channel CTRL when theUEH uses the TD downlink symbols.

Next, a transmission method of an uplink HARQ feedback for a downlinkpacket is described with reference to FIG. 14 and FIG. 15.

FIG. 14 and FIG. 15 each show a method of transmitting an uplink HARQfeedback in a wireless communication system according to an embodimentof the present invention. The uplink HARQ feedback for each transportblock may be an uplink HARQ ACK or an uplink HARQ NACK. For convenience,the uplink HARQ feedback is shown as an HARQ ACK in FIG. 14 and FIG. 15.

Referring to FIG. 14, a base station may transmit a downlink packet in adownlink time duration of an ST subframe and receive an uplink HARQfeedback in an uplink time duration of the same subframe. When the basestation transmits downlink packets having different symbol indexoffsets, for example a downlink packet DLP1 following a downlink controlchannel CTRL including a downlink assignment and a downlink packet DPL2having a symbol index offset DL_Offset being greater than zero, on inthe same subframe, a terminal demodulates the downlink packet DLP1following the downlink control channel CTRL and generates an uplink HARQfeedback in accordance with an effective timing advance TA₁. Further,the terminal UE demodulates the downlink packet DLP2 having the symbolindex offset DL_Offset and generates an uplink HARQ feedback inaccordance with an effective timing advance TA₂. In some embodiments,the base station may allocate different radio resources to the twouplink HARQ feedbacks using a TDM scheme or an FDM scheme so that thebase station can receive the two uplink HARQ feedback without collision.It is shown in FIG. 14 that different subcarriers are allocated to thetwo uplink HARQ feedbacks using the FDM scheme. The terminal UE canidentify the radio resources necessary for the uplink HARQ feedbacktransmission from an uplink grant of the downlink control channel CTRL.

Referring to FIG. 15, a base station may receive an uplink HARQ feedbackin the n-th subframe for a downlink packet DLP1 transmitted in the(n-k)-th subframe. Here, n and k are integers greater than or equal to0. A feedback timing k indicating the delayed HARQ feedback timing maybe informed to a terminal by the base station through a higher layerconfiguration or dynamic signaling (e.g., a downlink control channel),or their combination. In one embodiment, the base station may configureone value for the terminal through the higher layer signalling. Inanother embodiment, the base station may configure a plurality offeedback timing values k for the terminal through the higher layersignalling and indicate any one of the feedback timing values k throughthe dynamic signaling.

In some embodiments, the feedback timing value k may be configureddifferently for each downlink packet. For example, the feedback timingvalue k may be set to zero for a low-latency downlink packet DLP2 andthe feedback timing value k may be configured to an integer beinggreater than or equal to one for a high-latency downlink packet DLP1.Therefore, as shown in FIG. 15, the base station may receive the uplinkHARQ feedback in the n-th subframe for another downlink packet (forexample, the low-latency downlink packet DPL2) transmitted in the n-thsubframe.

In this manner, when a plurality of uplink HARQ feedbacks aretransmitted in one ST subframe, the base station may allocate radioresources required for uplink HARQ feedback transmission according tothe number of uplink HARQ feedbacks. The terminal may maintain thenumber of uplink HARQ feedbacks by performing multiplexing or mayperform a bundling operation to reduce the number of uplink HARQfeedbacks. In one embodiment, the base station may configure either themultiplexing or bundling to the terminal through a higher layersignalling.

In some embodiments, when the base station sets HARQ feedback bundlingfor the terminal, the base station may inform the terminal of the numberof uplink HARQ feedbacks to be transmitted by the terminal through thedownlink assignment. The terminal may compare the number of receiveddownlink packets with the number of uplink HARQ feedbacks informed bythe base station and may regard that it fails to demodulate the downlinkassignment if the two numbers are different from each other.

On the other hand, the HARQ feedback timing for the low-latency downlinkpacket may be 0 and the HARQ feedback timing for the high-latencydownlink packet may be k. In this case, if terminal receives thehigh-latency downlink packet in the (n-k)-th subframe and receivesanother high-latency downlink packet and the low-latency downlink packetin the n-th subframe, the terminal may transmit an HARQ feedback for thehigh-latency downlink packet of the (n-k)-th subframe and an HARQfeedback for the low-latency downlink packet of the n-th subframe in then-th subframe and transmit an HARQ feedback for the high-latencydownlink packet of the n-th subframe in the (n+k)-th subframe. In thiscase, the terminal may bundle the two HARQ feedbacks in the n-thsubframe.

Next, a method of transmitting an uplink packet using a radio frameaccording to an embodiment of the present invention is described withreference to FIG. 16 to FIG. 19.

FIG. 16, FIG. 17, FIG. 18, and FIG. 19 each show an uplink transmissionmethod in a wireless communication system according to an embodiment ofthe present invention.

When a terminal transmits an uplink packet in an uplink time duration ofan ST subframe to a base station, the base station may transmit adownlink HARQ feedback in a downlink time duration of the same STsubframe. The downlink HARQ feedback may be a downlink HARQ ACK or adownlink HARQ NACK. For convenience, the downlink HARQ feedback is shownas an HARQ ACK in FIG. 16 to FIG. 19.

Referring to FIG. 16, FIG. 17, FIG. 18, and FIG. 19, the base stationtransmits an uplink grant to the terminal through a downlink controlchannel CTRL, and the terminal transmits an uplink packet ULP based onthe uplink grant. As shown in FIG. 16 and FIG. 17, the uplink packet ULPmay be transmitted in the uplink time duration of the ST subframe inwhich the downlink control channel CTRL including the uplink grant istransmitted. Alternatively, as shown in FIG. 18 and FIG. 19, the uplinkpacket ULP may be transmitted in an ST subframe (for example, subframe(n+k)) different from the ST subframe (for example, subframe n) in whichthe control channel CTRL including the uplink grant is transmitted. Asshown in FIG. 16 and FIG. 18, the control channel CTRL including theuplink grant may be transmitted through a beginning downlink symbol(s)of the ST subframe. Alternatively, as shown in FIG. 17 and FIG. 19, thecontrol channel CTRL including the uplink grant may be transmitted inthe same symbols as a downlink packet for other terminals in the STsubframe.

In some embodiments, a size of an uplink packet may be limited to apredetermined size or less in order to transmit a downlink HARQ feedbackfor the uplink packet in the same subframe as the uplink packet. To thisend, a base station may segment the uplink packet so that the size ofeach uplink packet can become the predetermined size or less. Then, atime required for a base station to decode the uplink packet can bereduced. In this case, the base station may allocate a radio resourcecorresponding to a small number of uplink symbols such that a shortpacket can be confined to a short time and use a sufficient bandwidth,and schedule the radio resource to the terminal. In one embodiment, thenumber of uplink symbols to be applied to short packet scheduling may beconfigured through a higher layer signalling. In this case, the numberof uplink symbols may be implicitly or explicitly indicated. Forexample, the number of UL symbols may be implicitly indicated in amanner of predetermined number of UL symbols according to traffic typesand explicitly indicating a specific traffic type, or the number of ULsymbols may be explicitly indicated. In another embodiment, the numberof UL symbols to be applied to the short packet scheduling may beincluded in the downlink assignment. Those set of uplink symbols maycorrespond to an uplink sub-slot.

Next, a method of transmitting a downlink HARQ feedback for an uplinkpacket is described with reference to FIG. 20 to FIG. 22

FIG. 20 shows another example of an ST subframe structure in a wirelesscommunication system according to an embodiment of the presentinvention, and FIG. 21 and FIG. 22 each show a method of transmitting adownlink HARQ feedback in a wireless communication system according toan embodiment of the present invention. The downlink HARQ feedback maybe a downlink HARQ ACK or a downlink HARQ NACK. For convenience, thedownlink HARQ feedback is shown as an HARQ ACK in FIG. 21 and FIG. 22.

In some embodiments, to support a low-latency uplink traffic, a terminalmay transmit an uplink packet after demodulating a downlink assignmentand receive a downlink HARQ feedback in the same ST subframe. To thisend, as shown in FIG. 20, the ST subframe may further include a downlinktime duration DwPTS2 after an uplink time duration UpPTS. That is, theST subframe may include a downlink time duration DwPTS1, a guard periodGP, an uplink time duration UpPTS, and a downlink time duration DwPTS2.Therefore, the terminal may demodulate a downlink control channel CTRLtransmitted in the first downlink time duration DwPTS1, transmit theuplink packet in the uplink time duration UpPTS, and then receive adownlink HARQ feedback in the second downlink time duration DwPTS2.Consequently, the terminal can support the low-latency uplink traffic.

As described in the uplink HARQ feedback, a value k indicating HARQfeedback timing may be set to zero or an integer being greater than orequal to one. As shown in FIG. 21, a base station may receive an uplinkpacket and then transmit a downlink HARQ feedback in the same subframe.Alternatively, as shown in FIG. 22, the base station may receive anuplink packet in the n-th subframe and then transmit a downlink HARQfeedback for the uplink packet in the (n+k)-th subframe.

When using the downlink HARQ feedback, the terminal stores an uplinkpacket which has been already transmitted and then performretransmissions or not depending on a demodulation result at the basestation which can be known to the terminal through the downlink HARQfeedback. If the downlink HARQ feedback is ACK, the terminal does notneed to keep the uplink packet stored in a buffer, and thus deletes theuplink packet from the buffer. If the downlink HARQ feedback is NACK,the terminal may hold the stored uplink packet stored during apredetermined time for retransmission.

In some embodiments, the base station may not transmit a downlink HARQfeedback for an uplink packet transmitted by the terminal. In this case,the terminal may manage the buffer according to an uplink grant. If thebase station succeeds in demodulating the uplink packet, the basestation schedules a new uplink packet. At this time, the base stationmay schedule the new uplink packet using the same identifier (ID), forexample, the same HARQ process ID. Then, the terminal may not store theuplink packet stored in the buffer any longer, and store the new uplinkpacket. On the other hand, if the base station fails to demodulate theuplink packet, the base station schedules to retransmit the same uplinkpacket but with different redundancy version. At this time, the basestation may schedule the uplink packet using the same ID, for example,the same HARQ process ID. Then, the terminal can maintain the uplinkpacket stored in the buffer during a predetermined time for a possibleretransmission.

In some embodiments, a base station may configure an ST subframe foreach terminal. This embodiment is described with reference to FIG. 23.

FIG. 23 shows a terminal-specific ST subframe in a wirelesscommunication system according to an embodiment of the presentinvention.

Referring to FIG. 23, in some embodiments, the base station mayconfigure a terminal-specific ST subframe. FIG. 23 shows an example inwhich the base station configures different terminal-specific STsubframes for the two terminals UE1 and UE2. In one embodiment, the basestation may configure the terminal specific ST subframe through a higherlayer signaling.

In the two ST subframes for the terminals UE1 and UE2, downlink controlchannels CTRL may be indicated to have the same time duration. Lengthsof the downlink time durations DwPTS or lengths of the uplink timedurations UpPTS may be configured differently according to the terminalsUE1 and UE2.

In one embodiment, the base station may adjust a ratio between thedownlink time duration DwPTS and the uplink time duration UpPTS inconsideration of a ratio between the downlink traffic and the uplinktraffic for the terminals UE1 and UE2.

In one embodiment, the downlink time duration DwPTS may defined from thebeginning of the ST subframe, and the uplink time duration UpPTS may bedefined from the end of the ST subframe. In this case, a time durationexcluding the downlink time duration DwPTS and the uplink time durationUpPTS corresponds to a guard period GP. In one embodiment, when adownlink packet duration DL1 or DL2 or an uplink packet duration UL1 orUL2 allocated to a certain terminal corresponds to a part of thedownlink time duration DwPTS or the uplink time duration, the BS mayadjust a gap between reception of the downlink packet DL1 or DL2 andtransmission of the uplink packet UL1 or UL2 by adjusting a start symboloffset of the downlink packet duration or the uplink packet duration. Inthis case, the base station may adjust the gap according to processingcapability of the terminal.

Then, the guard period interpreted by the base station may correspond toa time duration in which all terminals may regard as the gaps, and maybe located in the middle of the subframe. The length of the guard periodGP may be determined by the base station and may be zero. Even if thelength of the guard period GP is zero, the terminal can exploit a timecorresponding to the gap between the reception end point of the downlinkpacket and the transmission timing of the uplink packet.

When the downlink packet durations of the terminals UE1 and UE2 aredifferent from each other or start symbol offsets are different fromeach other, a downlink symbol on which the downlink packets DL1 and DL2overlap with each other or a downlink symbol on which the downlinkpackets DL1 and DL2 do not overlap with each other may exist. Since aninter-cell interference may change during transmission of the downlinkpackets DL1 and DL2, the base station may perform scheduling forinterference management. Similarly, when the uplink packet duration UL1and UL2 of the two terminals UE1 and UE2 are different from each otheror start symbol offsets are different from each other, an uplink symbolon which the uplink packets UL1 and UL2 overlap with each other or anuplink symbol on which the uplink packets UL1 and UL2 do not overlapwith each other may exist. Since an inter-cell interference may changeduring transmission of the uplink packets UL1 and UL2, the base stationmay perform scheduling for interference management.

As described above, when the base station configures the ST subframethrough the higher layer signalling, the base station may reconfigure adownlink time duration and an uplink time duration of the ST subframefor the terminal using another higher layer signaling in order to changethe ST subframe configuration. This method cannot adapt quickly to achange in the ratio between the downlink traffic and the uplink trafficgenerated in the ST subframe. In case of using a dynamic TDD in awireless communication system operating in an unpaired spectrum, it isnecessary to adjust the ratio between a downlink resource and an uplinkresource more quickly. Accordingly, in some embodiments, the basestation may control the downlink resource and the uplink resource basedon the downlink control channel rather than the higher layer signaling.

FIG. 24 is a flowchart showing a method of scheduling an ST subframe ina wireless communication system according to an embodiment of thepresent invention.

Referring to FIG. 24, in some embodiments, a base station may notconfigure a downlink time duration and an uplink time duration of an STsubframe in advance. Accordingly, the base station transmits informationon a downlink packet duration through a downlink assignment of adownlink control channel (S2410), and transmits information on an uplinkpacket duration through an uplink grant of the downlink control channel(S2420). Then, a terminal can receive a downlink packet in the downlinkpacket duration and transmit an uplink packet in the uplink packetduration without recognizing a specific position of a guard periodwithin the subframe.

In some embodiments, the base station may notify the terminal of atiming k for indicating a transmission timing used by the terminal. Inthis case, the base station may inform the timing k through the higherlayer signaling or a DCI of the downlink control channel, or theircombination.

In one embodiment, when the base station configures a downlinktransmission mode through a higher layer signaling, the base station mayindicate the timing k for transmitting an uplink HARQ feedback and anuplink duration for the uplink HARQ feedback. In this case, the terminalcan know the transmission timing of the uplink HARQ feedback as the k-thsubframe after receiving the downlink control channel. That is, when thedownlink control channel is transmitted in subframe n, the terminal canidentify subframe (n+k) as the transmission timing of the uplink HARQfeedback. In another embodiment, if the base station separatelytransmits a timing k_(DL) through the DCI of the downlink controlchannel in subframe n, the terminal may transmit the uplink HARQfeedback in subframe (n+k_(DL)). In this case, the downlink controlchannel may include information on the uplink duration for transmittingthe uplink HARQ feedback.

In one embodiment, when the base station configures an uplinktransmission mode through the higher layer signaling, the base stationmay configure a timing k for transmitting uplink data and an uplinkduration for the uplink data. In this case, the terminal can know thetransmitting timing of the uplink data as the k-th subframe afterreceiving the downlink control channel. That is, when the downlinkcontrol channel is transmitted in subframe n, the terminal can identifysubframe (n+k) as the transmission timing of the uplink data. In anotherembodiment, if the base station separately transmits a timing k_(UL)through the DCI of the downlink control channel in subframe n, theterminal may transmit the uplink data in subframe (n+k_(UL)). In thiscase, the downlink control channel may include information on the uplinkpacket duration for transmitting the uplink data.

In some embodiments, the timing k may be implicitly configured to zeroin a wireless communication system for a low latency communication andmay not be configured explicitly through the DCI of the downlink controlchannel. Then, the terminal may transmit the uplink HARQ feedback or theuplink data using an uplink packet duration configured by a downlinkassignment and an uplink grant, respectively, in the same subframe as asubframe where the downlink control channel is received.

In some embodiments, a guard period may be removed from the ST subframe.Hereinafter, such an embodiment is described with reference to FIG. 25to FIG. 28.

FIG. 25 and FIG. 26 each show an ST subframe without a guard interval ina wireless communication system according to an embodiment of thepresent invention, FIG. 27 shows a transmission timing using an STsubframe in a wireless communication system according to an embodimentof the present invention. ST subframe, and FIG. 28 shows an ST subframeconfigured for each subband in a wireless communication system accordingto an embodiment of the present invention.

In some embodiments, a base station may configure terminal-specific STsubframes to a plurality of terminals. In this case, the base stationmay configure a terminal-specific downlink TTI and a terminal-specificuplink TTI to each of the terminals. In one embodiment, the base stationmay configure the terminal-specific ST subframe through a higher layersignaling or a downlink control channel, or their combination. In oneembodiment, the base station may configure a downlink time duration, anuplink time duration, and a guard period through the higher layersignaling in an ST subframe configuration, and may configure a downlinkpacket duration and an uplink packet duration through the higher layersignaling in a transmission mode configuration. In another embodiment, adownlink assignment may include information on the downlink packetduration and an uplink grant may include information on the uplinkpacket duration.

In this case, guard periods having different lengths may be indicated tothe terminals, and the base station may determine the downlink packetduration and the uplink packet duration to each terminal inconsideration of the downlink coverage and the uplink coverage.

Referring to FIG. 25 and FIG. 26, it is assumed that a base stationperforms a downlink assignment to a terminal UE1 and performs an uplinkgrant to another terminal UE2. Then, a guard period may exist between adownlink packet duration DL21 of the terminal UE1 and an uplink packetduration UL22 of the terminal UE2. In this case, the base station mayperform scheduling for other terminal UE3 at a time durationcorresponding to the guard period. The base station may perform adownlink assignment of a downlink packet duration DL23 and an uplinkgrant of an uplink packet duration UL23 for the terminal UE3 during thetime duration corresponding to the guard period as shown in FIG. 25.Alternatively, as shown in FIG. 26, the base station may perform anuplink scheduling of an uplink packet duration UL23 and a downlinkassignment of a downlink packet duration DL23 for the terminal UE3.

In this case, no interference among the terminals UE1, UE2, and UE3 mayoccur due a propagation delay difference and a timing advancedifference. As shown in FIG. 26, when the terminal UE1 performsreception and the terminal UE3 performs transmission, no interferencemay occur since the reception of the terminal UE1 has already beencompleted at the transmission time of the terminal UE3 due to apropagation delay between the terminals UE1 and UE3. In addition, asshown in FIG. 25, when the terminal UE3 performs transmission afterreception, if the propagation delay is negligibly small, the terminalUE3 may not perform the transmission and reception at the same time.That is, the terminal UE3 may satisfy the half duplex constraint. Forexample, if the terminal UE3 is located at a very close position of thebase station, the propagation delay and the timing advance of theterminal UE3 may be regarded as zero.

In FIG. 25 and FIG. 26, the uplink packet duration UL23 may be notallocated to the terminal UE3 but be allocated to other terminal UE4located at a position similar to the terminal UE3 through the uplinkgrant. No intra-cell interference may occur even when the downlinkpacket duration DL23 is allocated to the terminal UE3 and the uplinkpacket duration UL23 is allocated to the terminal UE4.

Meanwhile, it may be considered a case where the propagation delay andthe timing advance of the terminal UE 3 are smaller than half of acyclic prefix (CP) length of CP-based OFDM (CP-OFDM). In an LTE system,since half of the normal CP is 2.3437 μs[=(144/2)*Ts=(144/2)*(1/(2048*15000))], a value (=703.125 m) obtained bymultiplying half of the normal CP by the speed of light is the coveragewhen the half of the CP length is used. In a case of dense urban areasof LTE or 5G NR (new radio), an inter-site distance may be considered as200 m. Therefore, the coverage in a real communication environment maybe within half of the normal CP of the LTE system. In this case, theterminal UE 3 may experience an inter-symbol interference in some delayspread. In the case where the terminal UE 3 receives the inter-symbolinterference, the received intra-symbol interference is a signal of theterminal UE3 itself, the terminal UE3 may perform equalization in thereception process or the base station may adjust the MCS to removeinterference effects.

As such, the base station may configure the terminal-specific STsubframe to the terminal through a higher layer signaling. Further, thebase station may configure a downlink packet duration having a length ofTD2 i to a terminal UEi. In this case, the base station may transmit astart symbol index to the terminal UEi through a higher layer signaling,a DCI of a downlink control channel, or a combination thereof.Furthermore, the base station may configure an uplink packet duration oflength TU2 i to the terminal UEi. In this case, the base station maytransmit a start symbol index to the terminal UEi through a higher layersignaling, a DCI of a downlink control channel, or a combinationthereof. Therefore, a length GP2 i of a guard period for the terminalUEi can be adjusted through the downlink assignment and the uplink grantby the base station BS.

In another embodiment, the base station may indicate the downlink packetduration and the uplink packet duration using only the downlink controlchannel without using the higher layer signaling.

In some embodiments, the base station may configure the same ST subframefor the terminals. The ST subframe may not include a guard period butmay include only a downlink packet duration and an uplink packetduration. That is, the base station may not configure a cell-specificguard period. Then, the base station may, by implementation, guarantee aterminal-specific guard period to the terminal such that the terminalcan acquire a processing latency.

As such, since all the terminals commonly receive the downlink controlchannel but the respective terminals may have downlink packet durationsor uplink packet durations having different lengths, the base stationcan flexibly perform scheduling such that throughput can be improved.

However, the downlink packet duration DL2 i of a certain terminal UEiand an uplink packet duration UL2 j of other terminal UEj may interferewith each other. This is because the downlink packet duration DL2 i ofthe terminal UEi and the uplink packet duration UL2 j of the terminalUEj may overlap in time when a timing advance is largely applied to theterminal UEj. Similarly, interference may occur between the downlinkpacket duration DL2 i and an uplink packet duration UL2 i of the sameterminal UEi. In order to prevent performance deterioration due to suchthe interference, the base station may schedule the downlink packetdurations and the uplink packet durations according to the timingadvance distribution of the terminals UEi and UEj.

It is assumed that terminals located close to a base station have thesame propagation delay PDc and the same timing advance TAc and terminalslocated far from a base station have the same propagation delay PDe andthe same timing advance TAe. Here, the propagation delay PDe is greaterthan the propagation delay PDc. It is shown in FIG. 27 that terminalsUE1 and UE3 are located close to the base station DEV1, terminals UE2and UE4 are located far from the base station, the terminals UE1 and UE2operate in downlink, and the terminals UE3 and UE4 operation in uplink.Further, a downlink packet duration TD21 is allocated to the downlink ofthe terminal UE1, a downlink packet duration TD22 following the downlinkpacket duration TD21 is allocated to the downlink of the terminal UE2,an uplink packet duration TU23 is allocated to the uplink of theterminal UE3, and an uplink packet duration TU24 following the uplinkpacket duration TU23 is allocated to the uplink of the terminal UE4.

Then, the terminal UE1 receives a downlink control channel CTRL afterthe propagation delay PDc, and then receives a downlink packet in thedownlink packet duration TD22. The terminal UE2 receives the downlinkcontrol channel CTRL after the propagation delay PDe and then receives adownlink packet in the downlink packet duration TD21. The terminal UE3receives the downlink control channel CTRL after the propagation delayPDc and then transmits an uplink packet in the uplink packet durationTU23 in accordance with an effective timing advance ETA3. The effectivetiming advance ETA3 may be determined by reflecting an uplink symbolindex offset (0 in the example of FIG. 26) to a timing advance TA3, andthe timing advance TA3 may be determined in consideration of thepropagation delay PDc. The terminal UE4 receives the downlink controlchannel CTRL after the propagation delay PDe and then transmits anuplink packet in the uplink packet duration TU24 in accordance with aneffective timing advance ETA4. The effective timing advance ETA4 may bedetermined by reflecting an uplink symbol index offset (TU23 in theexample of FIG. 27) to a timing advance TA4, and the timing advance TA4may be determined in consideration of the propagation delay PDe.

In this case, as shown in FIG. 27, since the two terminals UE1 and UE3have the same propagation delay PDc, the uplink packet transmitted bythe terminal UE3 may affect the downlink packet received by the terminalUE2 during a certain time interval 123. That is, the terminal UE3 maycause an inter-cell interference to the terminal UE2. However, since theuplink packet transmitted by the terminal UE4 arrives at the terminalUE2 after the propagation delay difference (PDe-PDc) between the twoterminals UE4 and UE2, the uplink packet of the terminal UE4 may havelittle effect on the downlink packet of the terminal UE2. Therefore, ifthe time interval 123 described above is small enough, e.g., within thecyclic prefix, the terminals UE1 to UE4 can communicate without theintra-cell interference.

In one embodiment, if the time interval 123 is smaller than the cyclicprefix, the base station may not allocate a cell-specific guard periodsymbol in that subframe or slot.

In another embodiment, if the time interval 123 is greater than thecyclic prefix, the base station may allocate a guard period to preventthe interference. The guard period may be allocated specifically to theterminal. Various methods of allocating the guard period are describedbelow.

According to one method, the base station may reduce the downlink packetduration TD22 allocated to the terminal UE1 to allocate the guardperiod. For example, the base station may reduce the downlink packetduration TD22 by the time interval 123, from the downlink-uplinkswitching boundary, and configure the guard period GP as long as thereduced duration of TD22. To this end, the base station may transmitinformation on the guard period GP to the terminal UE1 through adownlink assignment of the downlink control channel. Alternatively, thebase station may transmit information on the reduced downlink packetduration TD22 to the terminal UE1.

According to another method, the base station may reduce the uplinkpacket duration TU23 allocated to the terminal UE3 to allocate the guardperiod. For example, the base station may reduce the uplink packetduration TU23 by the time interval 123, from the downlink-uplinkswitching boundary, and configure the guard period GP as long as thereduced duration of TU23. To this end, the base station may transmitinformation on the guard period GP to the terminal UE3 through an uplinkgrant of the downlink control channel. Alternatively, the base stationmay transmit information on the reduced uplink packet duration to theterminal UE3.

According to yet another method, the base station may reduce both thedownlink packet duration TD22 allocated to the terminal UE1, and theuplink packet duration TU23 allocated to the terminal UE3, to allocatethe guard period. For example, the base station may reduce the downlinkpacket duration TD22 and the uplink packet duration TU22 by the timeinterval 123, and configure the guard period GP as long as the reduceddownlink and uplink durations TD22 and TU22. To this end, the basestation may transmit information on the guard period GP to the terminalUE2 through the downlink allocation of the downlink control channel, andtransmit the information on the guard period GP to the terminal UE3through the uplink grant of the downlink control channel. Alternatively,the base station may transmit the information on the reduced downlinkpacket duration' to the terminal UE2, and transmit the information onthe reduced uplink packet duration to the terminal UE3.

According to still another method, as shown in FIG. 28, differentmethods may be applied to a plurality of schedulable subbands belongingto the same ST subframe. In this case, the cell-specific guard periodmay not be allocated, and the guard period GP in each subband may beallocated to the ST subframe in each corresponding subband. Referring toFIG. 28, a guard period GP1 is allocated to a part of a downlink timeduration DwPTS in subband 1, a guard period GP2 is allocated to a partof the downlink time duration DwPTS and a part of an uplink timeduration UpPTS in subband 2, and a guard period GP3 is allocated to apart of the uplink time duration UpPTS in subband 3.

While an example that where a downlink control channel CTRL istransmitted in a wide band is shown in FIG. 28, but the downlink controlchannel CTRL may be defined in each subband independently and also betransmitted in each subband.

As described above, when a large amount of traffic is processed in thewireless communication system, a larger amount of traffic can beprocessed by not setting the cell-specific guard period.

Next, various examples of a transmission method using an ST subframe aredescribed with reference to FIG. 29 to FIG. 31.

FIG. 29 shows an example of a transmission method using a plurality ofscheduling types in a wireless communication system according to anembodiment of the present invention, and FIG. 30 and FIG. 31 each showan example of a low-latency traffic transmission method in a wirelesscommunication system according to an embodiment of the presentinvention.

Referring to FIG. 29, a base station may have a plurality of schedulingtypes. The plurality of scheduling types may include a type Ltransferring low latency traffic and a type H transferring high latencytraffic.

When a terminal demodulates a downlink control channel CTRL anddetermines that a scheduling type is type L, the terminal demodulates adownlink packet DLPL for the low latency traffic in a downlink packetduration TD₁ corresponding to type L. The downlink packet duration TD₁may be detected through a higher layer signaling or a downlinkassignment of the downlink control channel CTRL, or their combination.For example, the downlink packet DLPL for the low latency traffic may betransmitted in succession to the downlink control channel CTRL. Theterminal may transmit an uplink HARQ feedback for the downlink packetDLPL for the low latency traffic in the same subframe (subframe n) asthe downlink packet DLPL. Further, when the downlink control channelCTRL delivers an uplink grant for the low latency traffic, the terminalmay transmit an uplink packet ULP in the same subframe (subframe n) asthe downlink control channel CTRL.

When the terminal demodulates the downlink control channel CTRL anddetermines that the scheduling type is type H, the terminal demodulatesa downlink packet DLPH for the high latency traffic in a downlink packetduration TD₂ corresponding to type H. The downlink packet duration TD₂may be detected through the higher layer signaling or the downlinkassignment of the downlink control channel CTRL, or their combination.For example, the downlink packet for the high latency traffic may betransmitted in the downlink packet duration TD₂ following the downlinkpacket duration TD₁ allocated to the downlink packet for the low latencytraffic. The terminal may transmit an uplink HARQ feedback for thedownlink packet DLPH for the high latency traffic in a subframe(subframe n) after k subframes from a subframe (subframe (n-k)) wherethe downlink packet DLPH is received.

In some embodiments, a base station may transmit a downlink controlchannel CTRL by including a value k indicating an HARQ feedback timingto the downlink assignment. For example, if the k value is zero, aterminal may transmit an HARQ feedback in a subframe where a downlinkpacket is received. If the k value is one or more, the terminal maytransmit the HARQ feedback after k subframes from a subframe where thedownlink packet is received.

In some embodiments, a base station may not perform a downlink HARQfeedback. In this case, the base station demodulates an uplink packettransmitted from a terminal and does not transmit an HARQ ACK to theterminal when the demodulation is successful. Since the terminal may beindicated to retransmit the same uplink packet through a uplink grantfrom the base station within a predetermined time window, the terminalmay not discard the uplink packet before the predetermined time expires.If the base station fails to demodulate the uplink packet, base stationdoes not need to transmit an HARQ NACK to the terminal. Instead, thebase station may request the same uplink packet of possibly differentredundancy version to the terminal through an uplink grant.

A case where only low latency traffic exists is described. In this case,one ST subframe may support all of downlink transmission, uplinktransmission, and an uplink HARQ feedback.

Referring to FIG. 30, a base station may transmit a downlink assignmentto a terminal UE1 and an uplink grant to a terminal UE2 through adownlink control channel. The base station may transmit downlink controlchannels CTRL1 and CTRL2 twice.

The terminal UE1 may receive the downlink control channel CTRL1, forexample, in a symbol with symbol index 0. A downlink packet durationindicated by the downlink control channel CTRL1 may be, for example,four symbols from symbol index 1, and a duration corresponding to anHARQ feedback may be, for example, a symbol with symbol index 9. Then,the terminal UE1 receives a downlink packet DLP1 on the four symbolsstarting from symbol index 1, and transmits an uplink HARQ feedback onthe symbol with symbol index 9. The base station may determine whetherto perform retransmission of the downlink packet DLP1 based on theuplink HARQ feedback.

When the base station further transmits a low latency traffic to theterminal UE1, the base station may further transmit the downlink controlchannel CTRL2 on a symbol with a predetermined symbol index (e.g.,symbol index 6). Then, the terminal can receive the downlink controlchannel CTRL2 on the predetermined symbol with symbol index 6. Adownlink packet duration indicated by the downlink control channel CTRL2may be, for example, a symbol with symbol index 7, and a durationcorresponding to an uplink HARQ feedback may be, for example, a symbolwith symbol index 13. Then, the terminal can receive a symbol downlinkpacket DLP2 on the symbol with symbol index 7 and can transmit an uplinkHARQ feedback on the symbol with symbol index 13.

When another terminal UE2 generates uplink traffic, the terminal UE2 mayreceive an uplink grant from the base station through the downlinkcontrol channel CTRL1. In this case, the terminal UE2 may havetransmitted a scheduling request SR to the base station in order torequest the uplink grant. Then, the terminal UE2 can transmit an uplinkpacket ULP1 in an uplink packet duration indicated by the uplink grant,for example, two symbols from symbol index 9 corresponding to aneffective timing advance.

When the base station receives an additional low latency traffic fromthe terminal UE2, the base station may transmit an uplink grant to theterminal UE2 in the downlink control channel CTRL2 transmitted in thepredetermined symbol index, e.g., symbol index 6. Then, the terminal UE2can transmit an uplink packet ULP2 in an uplink packet durationindicated by the uplink grant, for example, two symbols from symbolindex 11 corresponding to an effective timing advance.

In some embodiments, it may happen that the terminal UE2 generates lowlatency uplink traffic but cannot wait for a resource for the schedulingrequest allocated by the base station. Accordingly, the base station mayallocate to the terminal UE2 a predetermined uplink resource or apreconfigured uplink resource, i.e., an uplink packet duration, where anuplink packet can be transmitted without an uplink grant. Thus, theterminal UE2 may transmit an uplink packet ULP3 even if there is nouplink grant. The base station may allocate this uplink resource throughsemi-persistent (SP) scheduling. In this case, the base station mayperform the SP scheduling for one terminal but may perform the SPscheduling of the same uplink resources or uplink resources whose partbeing overlapped for a plurality of terminals.

Referring to FIG. 31, one ST subframe may include two slots. In thiscase, the base station may transmit a downlink assignment to a terminalUE1 through a downlink control channel CTRL1 in slot 0. Then, theterminal UE1 may receive a downlink packet DLP in a downlink packetduration (e.g., four symbols from symbol index 1) indicated by thedownlink control channel CTRL1 and transmit an HARQ feedback. The basestation may transmit an uplink grant to the terminal UE2 through adownlink control channel CTRL2 in slot 1. Then, the terminal UE2 maytransmit an uplink packet ULP in an uplink packet duration (e.g., foursymbols from symbol index 2) indicated by the downlink control channelCTRL2. Further, the terminal UE2 may transmit a scheduling request SR tothe base station for uplink transmission.

FIG. 32 shows a radio frame structure used in a wireless communicationsystem according to another embodiment of the present invention.

Referring to FIG. 32, a radio frame includes a plurality of subframes.Some subframes may be forward subframes and some subframes may bereverse subframes in the radio frame. One forward subframe and onereverse subframe are aggregated to form an aggregated subframe. It isshown in FIG. 32 that the radio frame includes ten subframes and the tensubframes form five aggregated subframes. Alternatively, only somesubframes in the radio frame may form the aggregated subframe. Inanother embodiment, the aggregated subframe may be formed in the orderof the reverse subframe and the forward subframe. In yet anotherembodiment, the aggregated subframe may be formed by at least somesubframes among ST subframes, downlink subframes, and uplink subframesinstead of the two ST subframes.

In some embodiments, the base station may inform the terminal of aforward subframe configuration and a reverse subframe configuration viaa higher layer signaling.

FIG. 33 shows forward subframe configurations in a radio frame structureaccording to another embodiment of the present invention, FIG. 34 showsreverse subframe configurations in a radio frame structure according toanother embodiment of the present invention, and FIG. 35 showsaggregated subframe configurations in a radio frame structure accordingto another embodiment of the present invention.

Referring to FIG. 33, a forward subframe includes a downlink timeduration DwPTS, an uplink time duration UpPTS following the downlinktime duration DwPTS, and a guard period GP between the downlink timeduration DwPTS and the uplink time duration UpPTS. The downlink timeduration DwPTS consists of consecutive transmission of downlink symbols,and the uplink time duration UpPTS consists of consecutive transmissionof uplink symbols. The downlink symbol and the uplink symbol may havedifferent modulation schemes, different numerologies, differentsubcarrier spacings, or different cyclic prefix lengths.

In FIG. 33, four forward subframe configurations (configuration 0,configuration 1, configuration 2, and configuration 3) are shown as anexample. The forward subframe configuration may be determined by alength of a downlink time duration DwPTS and a length of an uplink timeduration UpPTS. The forward subframe of configuration 0 does not includean uplink time duration but includes a downlink time duration DwPTS anda guard period GP following the downlink time duration DwPTS. Theforward subframe of configurations 1, 2, or 3 includes a downlink timeduration DwPTS and an uplink time duration UpPTS. The lengths of thedownlink time durations DwPTS and/or the lengths of the uplink timedurations UpPTS are different from each other. For convenience, only acase where the lengths of the uplink time durations UpPTS are differentis shown in FIG. 33. In this case, a guard period GP is located betweenthe downlink time slot DwPTS and the uplink time slot UpPTS, and thelength of the guard period GP may vary depending on a length differencesof the downlink time slots DwPTS and/or the uplink time durations UpPTS.

The base station estimates the guard period GP in consideration ofpropagation delay and delay spread. The base station may select one of aplurality of forward subframe configurations based on the estimatedguard period GP and inform the terminal of an index of the selectedforward subframe configuration. In some embodiments, the forwardsubframe configuration index may be transmitted as system information.In one embodiment, the forward subframe configuration index may beincluded as a cell-specific message of a downlink control channel. Then,the terminal can recognize the number of downlink symbols belonging tothe downlink time duration and the number of uplink symbols belonging tothe uplink time duration based on the received forward subframeconfiguration index.

If the forward subframe does not include a downlink time duration, theterminal in an idle state may not recognize that forward subframe sothat an initial access or radio resource management (RRM) measurement ofthe terminal may be inefficient. Thus, in some embodiments, all forwardsubframes may have a downlink time duration having at least a minimumlength. That is, a predetermined number of symbols in the forwardsubframe may always be allocated to downlink. Then, the terminal mayperform the RRM measurement using the predetermined number of symbols.Further, when a downlink control channel is transmitted with apredetermined number of symbols, the terminal can receive a forwardsubframe configuration included in the downlink control channel.

Referring to FIG. 34, a reverse subframe includes an uplink timeduration UpPTS and a downlink time duration DwPTS following the uplinktime duration UpPTS, and an additional time may be assigned between theuplink time duration UpPTS and the downlink time duration DwPTS. Thisadditional time may be used as a circuit switching time of the basestation, a physical downlink discovery channel, or a physical downlinkheader channel. The uplink time duration UpPTS consists of consecutivetransmission of uplink symbols and the downlink time duration DwPTSconsists of consecutive transmission of downlink symbols. The uplinksymbol and the downlink symbol may have different modulation schemes,different numerologies, different subcarrier spacings, or differentcyclic prefix lengths.

In FIG. 34, three reverse subframe configurations (configuration 0,configuration 1, and configuration 2) are shown as an example. Thereverse subframe configuration may be determined by a length of theuplink time duration UpPTS and a length of the downlink time durationDwPTS. In the reverse subframe of configuration 0, 1, or 2, the lengthof the uplink time duration UpPTS and/or the length of the downlink timeduration DwPTS are different for each other. For convenience, only acase where the lengths of the downlink time durations DwPTS aredifferent is shown in FIG. 34. In this case, the additional time betweenthe uplink time duration UpPTS and the downlink time duration DwPTS mayvary depending on the difference of the uplink time durations UpPTSand/or the downlink time duration DwPTS.

The base station may select one of a plurality of reverse subframeconfigurations and inform the terminal of an index of the selectedreverse subframe configuration. In some embodiments, the reversesubframe configuration index may be transmitted as system information.In one embodiment, the reverse subframe configuration index may beincluded as a cell-specific message of a downlink control channel. Then,the terminal can recognize the number of uplink symbols belonging to theuplink time duration UpPTS and the number of downlink symbols belongingto the downlink time duration DwPTS based on the received uplinksubframe configuration index.

The base station may transmit the downlink control channel in thedownlink time duration of the reverse subframe. The downlink controlchannel transmitted in the reverse subframe may not include acell-specific message. In this case, the terminal can be indicated for aresource allocation of the downlink control channel transmitted in thereverse subframe from the reverse subframe configuration.

If the reverse subframe does not include a downlink time duration, theterminal in an idle state may not recognize the reverse subframe so thatan initial access or RRM management of the terminal may be inefficient.Thus, in some embodiments, all reverse subframes may have a downlinktime duration having at least a minimum length. That is, a predeterminednumber of symbols in the reverse subframe may always be allocated todownlink. Then, the terminal may perform the RRM measurement with thepredetermined number of symbols. Further, when a downlink controlchannel is transmitted on the predetermined number of symbols, theterminal can receive the reverse subframe configuration included in thedownlink control channel.

Referring to FIG. 35, an aggregated subframe is a subframe in which aforward subframe and a reverse subframe are consecutively connected. Thesubframe includes a downlink time duration fDwPTS, uplink time durationsfUpPTS1 and rUpPTS2 following the downlink time duration fDwPTS, and adownlink time duration rDwPTS. A guard period GP may be located betweenthe downlink time duration fDwPTS and the uplink time duration fUpPTS orrUpPTS if the uplink time duration fUpPTS is not present.

In FIG. 35, three aggregated subframe configurations (configuration 0,configuration 1, and configuration 2) are shown as an example. Theaggregated subframe configuration may be determined by lengths of theuplink time durations fUpPTS and rUpPTS and the downlink time durationsfDwPTS and rDwPTS. For convenience, only a case where the lengths of theuplink time durations fUpPTS corresponding to the forward subframe aredifferent from each other is shown in FIG. 35. In this case, a length ofa guard period GP located between the downlink time duration fDwPTS andthe uplink time duration fUpPTS may vary depending on the aggregatedsubframe configurations or forward subframe configurations.

The terminal can know the number of downlink symbols and the number ofuplink symbols belonging to each of the forward subframe and the reversesubframe in the aggregated subframe through the aggregated subframeconfiguration.

Next, a downlink packet transmission method in a wireless communicationsystem according to another embodiment of the present invention isdescribed with reference to FIG. 36 and FIG. 37.

FIG. 36 and FIG. 37 each show a downlink transmission method in awireless communication system according to another embodiment of thepresent invention.

A base station using an aggregated subframe may transmit a downlinkcontrol channel in a forward subframe or a reverse subframe. In thiscase, the downlink control channel may coexist with a downlink packet ina TDM scheme or an FDM scheme. A DCI of the downlink control channel maybe transmitted using a distributed subcarrier set to obtain frequencydiversity, and may or may not use all of the system bandwidth.

The downlink control channel may transmit both or one of a cell-specificmessage and a terminal-specific message. System information may betransmitted in a physical broadcasting channel (PBCH) or in a downlinkpacket indicated by the downlink control channel.

In some embodiments, the downlink control channel may be allocated to asubband of the system bandwidth, i.e., some subcarriers, to improvedownlink throughput. Referring to FIG. 36, a downlink control channelfCTRL may be transmitted by using a time/frequency localized resource ina downlink time duration fDwPTS of a forward subframe. Referring to FIG.37, a downlink control channel rCTRL may be transmitted by using atime/frequency localized resource in a downlink time duration rDwPTS ofan uplink subframe.

If a large number of downlink symbols are included in the downlink timeduration fDwPTS of the forward subframe or the downlink time durationrDwPTS of the reverse subframe, a downlink control channel may betransmitted through only a subset of the downlink symbols such that timediversity can be obtained. However, when a small number of downlinksymbols are included in the downlink time duration fDwPTS or rDwPTS, thedownlink control channel may be transmitted on only a set of adjacentdownlink symbols since symbol index hopping within a coherence time isnot meaningful. For example, when the coherent time is defined as aduration of two downlink symbols, the time diversity can be obtained ifthe first and ninth symbols is used as a symbol subset for the downlinkcontrol channel in a downlink time duration having nine downlinksymbols. However, in a downlink time duration having two downlinksymbols, the time diversity cannot be obtained since all of the twosymbols are used for the downlink control channel for channel capacity.

Next, a downlink transmission method using an aggregated subframe formedin order of a reverse subframe and a forward subframe is described withreference to FIG. 38 and FIG. 39.

FIG. 38 and FIG. 39 each show a downlink transmission method using anaggregated subframe in a wireless communication system according toanother embodiment of the present invention.

In some embodiments, a downlink packet may be allocated in a downlinktime duration rDwPTS of a reverse subframe and a downlink time durationfDwPTS of a forward subframe following the downlink time duration rDwPTSin an aggregation subframe. One or two transport blocks may be assignedto this downlink packet and an HARQ feedback may be configured for eachtransport block.

When one transport block is allocated to the downlink packet, onetransport block may be allocated to the two downlink time durationsrDwPTS and fDwPTS such that a larger transport block can be used.Therefore, the base station can provide the higher downlink throughputto a terminal with low mobility.

However, since the two downlink time durations rDwPTS and fDwPTS towhich the downlink packet is allocated may have different interferenceconditions, an optimal MCS and precoding may be different for thedownlink time durations. Therefore, in some embodiments, the terminalmay decode the transport block while receiving one downlink packet,assuming that the MCS is the same for the two subframes but theprecoding may be different for the two subframes. In some embodiments,the terminal may decode the transport block while receiving one downlinkpacket, assuming that different antenna ports are allocated to thedownlink time durations but the same large scale fading is applied tothe downlink time durations.

In some embodiments, the downlink control channel fCTRL transmitted inthe downlink time duration of the forward subframe and the downlinkcontrol channel rCTRL transmitted in the downlink time duration of thereverse subframe may be defined by a type of the downlink controlchannel. In this case, referring to FIG. 38, a downlink packet fDLPtransmitted in the downlink time duration fDwPTS of the forward subframemay be associated with the downlink control channel fCTRL. A downlinkpacket rDLP transmitted in the downlink time duration rDwPTS of thereverse subframe or a downlink packet aDLP transmitted in downlink timedurations rDwPTS and fDwPTS of the aggregated subframe may be associatedwith the downlink control channel rCTRL.

Upon receiving the downlink control channel fCTRL in the forwardsubframe, the terminal may detect an assignment for the downlink packetfDLP. However, upon receiving the downlink control channel rCTRL in thereverse subframe, the terminal may not be able to determine whether anassignment for the downlink packet rDLP or an assignment for thedownlink packet aDLP is included. Accordingly, in one embodiment, a bitfor identifying the assignment for the downlink packet rDLP or theassignment for the downlink packet aDLP may be added to the downlinkcontrol channel rCTRL. This bit may have one bit and may indicate to theterminal whether to additionally receive the downlink packet in thefollowing forward subframe. In one embodiment, this bit may be added toa DCI of the downlink control channel rCTRL.

In some embodiments, the downlink time duration rDwPTS of the reversesubframe may be defined by a small number of downlink symbols as shownin FIG. 39. In this case, only the downlink control channel fCTRL of theforward subframe may be defined without defining a downlink controlchannel of the reverse subframe. Therefore, the downlink control channelfCTRL may include a downlink assignment for the downlink packet rDLP.

In some embodiments, the downlink control channel fCTRL may includestart symbol information of the downlink packet as the downlinkassignment, and the start symbol information may indicate a type of thedownlink packet. For example, if the start symbol information of thedownlink packet indicates the downlink time duration fDwPTS of theforward subframe, the terminal can recognize that the downlink packet isa downlink packet fDLP transmitted in the forward subframe. When thestart symbol information of the downlink packet indicates the downlinktime duration rDwPTS of the reverse subframe, the terminal may recognizethat the downlink pack is a downlink packet aDLP transmitted in theaggregated subframe or a downlink packet rDLP transmitted in the reversesubframe.

In one embodiment, when both the downlink packets aDLP and rDLP aredefined, the downlink control channel fCTRL may allocate end symbolinformation of the downlink packet as the downlink assignment todistinguish the downlink packets aDLP and rDLP. When the downlinkcontrol channel fCTRL includes the end symbol information of thedownlink packet, the terminal can recognize that the downlink packet isa downlink packet rDLP transmitted in the reverse subframe. In anotherembodiment, the downlink packet may be a downlink packet rDLP if the endsymbol information indicates the downlink time duration rDwPTS of thereverse subframe, and the downlink packet may be a downlink packet aDLPif the end symbol information indicates the downlink time durationfDwPTS of the following forward subframe.

In one embodiment, a DCI of the downlink control channel fCTRL may beused to indicate the start symbol information and the end symbolinformation.

In some embodiments, the downlink control channel fCTRL may include atype of the downlink packet as the downlink assignment instead ofincluding the start symbol information and the end symbol information.Therefore, when the type of the downlink packet indicates the downlinkpacket (fDLP) in the downlink control channel fCTRL, the terminal canreceive the downlink packet only in the downlink time duration fDwPTS ofthe forward subframe. When the type of the downlink packet indicates thedownlink packet rDLP, the terminal can receive the downlink packet onlyin the downlink time slot rDwPTS of the reverse subframe. When the typeof the downlink packet indicates the downlink packet a DLP, the terminalcan receive the downlink packet in the downlink time durations rDwPTSand fDwPTS of the reverse subframe and the subsequent forward subframe.

In one embodiment, the downlink control channel fCTRL may use two bitsto indicate the type of downlink packet.

A reference signal resource may be defined to allocate a downlink packetto a downlink time duration rDwPTS of a reverse subframe. Acell-specific reference signal CRS may be always transmitted in adownlink time duration, but a demodulation reference signal DMRS may betransmitted only when a downlink packet is transmitted.

Therefore, in some embodiments, if the DMRS is allocated to a downlinktime duration fDwPTS of a forward subframe in a case where the downlinkcontrol channel fCTRL allocates a downlink packet aDLP, the DMRStransmitted in the forward subframe may be used instead of allocating anadditional DMRS to the downlink time duration rDwPTS of the reversesubframe.

Next, an uplink transmission method using an aggregated subframe formedin order of a forward subframe and a reverse subframe is described withreference to FIG. 40 and FIG. 41.

FIG. 40 and FIG. 41 each show an uplink transmission method using anaggregated subframe in a wireless communication system according toanother embodiment of the present invention.

An uplink grant may be determined differently depending on processinglatency of a terminal. If the terminal encodes an uplink packet using ksubframe(s) and if a downlink control channel is received at subframe(subframe n), a timing of an uplink grant included in a downlink controlchannel fCTRL may be different from a timing of an uplink grant includedin a downlink control channel rCTRL. For example, Table 1 shows uplinkgrant timings in a case where uplink transmission is possible in asubframe where the uplink grant is received (a case where “k<1” isallowed) and a case where uplink transmission is possible in a subframefollowing a subframe where the uplink grant is received (a case of k=1).

TABLE 1 uplink grant timing uplink packet starting timing (subframe n)(subframe m) k < 1 fCTRL(n) fULP(n) or aULP(n) rULP(n + 1) k = 1 rCTRL(n− 1) fULP(n) or aULP(n) fCTRL(n) rULP(n + 1)

Referring to FIG. 40 and Table 1, the uplink grant may be transmittedvia a downlink control channel fCTRL of a forward subframe. If k is lessthan one, the downlink control channel fCTRL may indicate either anuplink packet fULP transmitted in an uplink time duration fUpPTS of thesame subframe or an uplink packet aULP transmitted in uplink timedurations fUpPTS and rUpPTS of the same subframe and a subsequentreverse subframe. In one embodiment, the downlink control channel fCTRLmay further include information for identifying either the uplink packetfULP or the uplink packet aULP. This information may have one bit and beadded to a DCI. Alternatively, the downlink control channel fCTRL mayindicate an uplink packet rULP transmitted in the uplink time durationsrUpPTS of the subsequent reverse subframe.

If k is one, the downlink control channel fCTRL may indicate an uplinkpacket rULP transmitted in an uplink time duration rUpPTS of a nextsubframe, i.e., a reverse subframe.

Referring to FIG. 41 and Table 1, the uplink grant may be transmittedvia a downlink control channel rCTRL of the reverse subframe. In thereverse subframe, since uplink transmission cannot be performed afterthe downlink control channel rCTRL is received, k<1 is not allowed.Therefore, the downlink control channel rCTRL may indicate either anuplink packet fULP transmitted in an uplink time duration fUpPTS of anext subframe, i.e., a forward subframe or an uplink packet aULPtransmitted in uplink time durations fUpPTS and rUpPTS of the forwardsubframe and a subsequent reverse subframe, i.e., an aggregatedsubframe. In one embodiment, the downlink control channel rCTRL mayfurther include information for identifying either the uplink packetfULP or the uplink packet aULP. This information may have one bit and beadded to the DCI.

As shown in FIG. 40 and FIG. 41, since one transport block is allocatedto two uplink time durations fUpPTS and rUpPTS for the uplink packetaULP transmitted in the aggregation subframe, a larger transport blockcan be used. Then, the base station can support higher uplink throughputto the terminal with low mobility. In a case where a terminal is locatedat a cell edge, the base station may allocate a narrow uplink bandwidthto the terminal and indicate a higher transmission power in order toacquire more uplink coverage.

However, since the two uplink time durations fUpPTS and rUpPTS formingthe uplink packet aULP may have different interference conditions, theoptimal MCS and precoding may be different for the uplink timedurations. In this case, the base station may decode the transport blockwhile receiving the uplink packet aULP, assuming that the MCS is thesame for the two subframes but the precoding may be different for thetwo subframes.

Next, a transmission method of an uplink HARQ feedback for a downlinkpacket using an aggregate subframe in a wireless communication systemaccording to another embodiment of the present invention is describedwith reference to FIG. 42 to FIG. 45.

FIG. 42, FIG. 43, FIG. 44 and FIG. 45 each show a method of transmittingan uplink HARQ feedback in a wireless communication system according toanother embodiment of the present invention. The uplink HARQ feedbackfor each transport block may be an uplink HARQ ACK or an uplink HARQNACK. For convenience, the uplink HARQ feedback is shown as an HARQ ACKin FIG. 42 to FIG. 45.

Referring to FIG. 42 and FIG. 43, a base station may transmit a downlinkcontrol channel fCTRL including a downlink assignment and a downlinkpacket fDLP in a downlink time duration fDwPTS of a forward subframe. Inthis case, when an uplink HARQ feedback timing indicates the samesubframe, a terminal may transmit an uplink HARQ feedback for thedownlink packet fDLP in an uplink time duration fUpPTS of the samesubframe as shown in FIG. 42. When the uplink HARQ feedback timingindicates a next subframe, the terminal may transmit the uplink HARQfeedback for the downlink packet fDLP in an uplink time duration rUpPTSof the next subframe (i.e., a reverse subframe) as shown in FIG. 43.

Referring to FIG. 44 and FIG. 45, a base station may transmit a downlinkcontrol channel rCTRL including a downlink assignment and a downlinkpacket in a downlink time duration rDwPTS of a reverse subframe. In thiscase, a downlink packet rDLP may be transmitted in the downlink timeduration rDwPTS of the reverse subframe, or a downlink packet aDLP maybe transmitted in the downlink time duration rDwPTS of the reversesubframe and an uplink time duration fDwPTS of the following forwardsubframe. Since there is no uplink time duration following the downlinktime duration rDwPTS of the reverse subframe, an uplink HARQ feedbacktiming cannot indicate the same subframe. When the uplink HARQ feedbacktiming indicates a next subframe, a terminal may transmit an uplink HARQfeedback for the downlink packet rDLP or aDLP in an uplink time durationfUpPTS of the next subframe (i.e., the forward subframe) as shown inFIG. 44. When the uplink HARQ feedback timing indicates a second nextsubframe, the terminal may transmit the uplink HARQ feedback for thedownlink packet rDLP (or aDLP) in an uplink time duration rUpPTS of thesecond next subframe (i.e., a next reverse subframe) as shown in FIG.45.

In one embodiment, the base station may indicate the uplink HARQfeedback timing through a higher layer signalling. In anotherembodiment, the base station may inform the terminal of the uplink HARQfeedback timing via a dynamic signaling. In yet another embodiment, thebase station may implicitly indicate the uplink HARQ feedback timing tothe terminal by selecting a DCI format.

Next, a method of transmitting a sounding reference signal in a wirelesscommunication system according to another embodiment of the presentinvention is described with reference to FIG. 46.

FIG. 46 shows a method of transmitting a sounding reference signal in awireless communication system according to another embodiment of thepresent invention.

Referring to FIG. 46, in some embodiments, a resource for a soundingreference signal SRS may be allocated for each uplink time durationUpPTS of an aggregated subframe. A terminal may transmit the soundingreference signal SRS in each uplink time duration for uplink channelestimation, and the base station may estimate an uplink channel based onthe sounding reference signal SRS. The base station may configure aperiodic sounding reference signal or an aperiodic sounding referencesignal to the terminal. In one embodiment, the base station mayconfigure the periodic sounding reference signal or the aperiodicsounding reference signal using a radio resource control (RRC)signalling.

In some embodiments, the terminal may perform rate matching on theuplink packet to reduce interference from the sounding reference signal.In one embodiment, in order to reduce a complexity of the rate matching,the terminal may transmit the sounding reference signal symbol on bothor one of the lower symbol index in the forward subframe and the highersymbol index in the reverse subframe as shown in FIG. 46. The basestation can allocate the uplink packet to consecutive uplink symbols byavoiding sounding reference signal resources located at the beginningand/or end of the uplink time durations fUpPTS and rUpPTS in theaggregated subframe. Therefore, a decoding probability of the uplinkpacket in the base station can be increased even in a mobile broadband(MBB) scenario in which a mobility of the terminal is high.

According to embodiments described above, in a wireless communicationsystem using an unpaired spectrum, downlink transmission and uplinktransmission can be simultaneously performed in one subframe.Accordingly, a low latency packet can be transmitted and an HARQfeedback can be performed in the same subframe.

While this invention has been described in connection with what ispresently considered to be practical embodiments, it is to be understoodthat the invention is not limited to the disclosed embodiments, but, onthe contrary, is intended to cover various modifications and equivalentarrangements included within the spirit and scope of the appendedclaims.

What is claimed is:
 1. A method of transmitting or receiving data by aterminal in a wireless communication system, the method comprising:receiving a first value indicating a transmission timing for an uplinkdata for the terminal from a base station through a higher layersignaling; receiving a downlink control channel from the base station ina downlink time duration of a first subframe, the downlink controlchannel including information on a downlink data duration allocated forthe terminal in the downlink time duration; receiving a downlink data inthe downlink data duration from the base station; and transmitting theuplink data for the terminal according to the first value indicating thetransmission timing for the uplink data for the terminal.
 2. The methodof claim 1, wherein when the first value indicates the first subframe,the downlink control channel further includes information on an uplinkdata duration allocated for the terminal in an uplink time duration ofthe first subframe, and the uplink data is transmitted by the terminalin the uplink data duration of the first subframe.
 3. The method ofclaim 1, wherein when the first value indicates a k-th subframe from thefirst subframe and k is an integer equal to or greater than 1, thedownlink control channel further includes information on an uplink dataduration allocated for the terminal in an uplink time duration of thek-th subframe, and the uplink data is transmitted by the terminal in theuplink data duration of the k-th subframe.
 4. The method of claim 1,wherein the downlink control channel further includes a second valueindicating a transmission timing for an acknowledgement or negativeacknowledgement (ACK/NACK) feedback for the downlink data.
 5. The methodof claim 4, wherein when the second value indicates the first subframe,the downlink control channel further includes information on an uplinkdata duration allocated for the terminal in the uplink time duration ofthe first subframe, and the ACK/NACK feedback for the downlink data istransmitted by the terminal in the uplink time duration of the firstsubframe.
 6. The method of claim 4, wherein when the second valueindicates an l-th subframe from the first subframe and l is an integerequal to or greater than 1, the downlink control channel furtherincludes information on an uplink data duration allocated for theterminal in an uplink time duration of the l-th subframe, and theACK/NACK feedback for the downlink data is transmitted by the terminalin the uplink time duration of the l-th subframe.
 7. A method oftransmitting or receiving data by a base station in a wirelesscommunication system, the method comprising: transmitting a first valueindicating a transmission timing for an uplink data for a terminal tothe terminal through a higher layer signaling; transmitting a downlinkcontrol channel to the terminal in a downlink time duration of the firstsubframe, the downlink control channel including information on adownlink data duration allocated for the terminal in the downlink timeduration; transmitting a downlink data in the downlink data duration tothe terminal; and receiving the uplink data for the terminal accordingto the first value indicating the transmission timing for the uplinkdata for the terminal.
 8. The method of claim 7, wherein when the firstvalue indicates the first subframe, the downlink control channel furtherincludes information on an uplink data duration allocated for theterminal in an uplink time duration of the first subframe, and theuplink data is received from the terminal in the uplink data duration ofthe first subframe.
 9. The method of claim 7, wherein when the firstvalue indicates a k-th subframe from the first subframe and k is aninteger equal to or greater than 1, the downlink control channel furtherincludes information on an uplink data duration allocated for theterminal in an uplink time duration of the k-th subframe, and the uplinkdata is received from the terminal in the uplink data duration of thek-th subframe.
 10. The method of claim 7, wherein the downlink controlchannel further includes a second value indicating a transmission timingfor an acknowledgement or negative acknowledgement (ACK/NACK) feedbackfor the downlink data.
 11. The method of claim 10, wherein when thesecond value indicates the first subframe, the downlink control channelfurther includes information on an uplink data duration allocated forthe terminal in the uplink time duration of the first subframe, and theACK/NACK feedback for the downlink data is received from the terminal inthe uplink time duration of the first subframe.
 12. The method of claim10, wherein when the second value indicates an l-th subframe from thefirst subframe and l is an integer equal to or greater than 1, thedownlink control channel further includes information on an uplink dataduration allocated for the terminal in an uplink time duration of thel-th subframe, and the ACK/NACK feedback for the downlink data isreceived from the terminal in the uplink time duration of the l-thsubframe.